Spiders in San Joaquin Valley Vineyards Pests, Biters, and IPM Agents
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Spiders in San Joaquin Valley Vineyards
Pests, Biters, and IPM Agents
By Devin Carroll
Revised 2012
Spiders play three roles in vineyards, depending on the species. Some
spiders are economic pests, some bite, and some are important predators of
vineyard pests. Some play all three roles.
Spiders become pests when they hide in bunches which may be boxed
and shipped to customers who do not appreciate finding spider carcasses in
their lunches. Large spiders are the chief concern here; most consumers are
not too dismayed when confronted with small spiders. A large spider can
also frighten or bother field workers.
Some spiders are also pests because they cover bunches with messy
webbing. Visible webbing can cause load rejection, even if spiders are not
found.
Fortunately spiders are very rarely found in grapes purchased at a
grocery store. I have never seen one, and no one I know has ever reported
one to me. Table grapes are carefully inspected twice, once by the picker
and once by the field packer, before they go in the box. They shake out the
spiders, especially any large spiders which tend to be on or near the surface.
But even if the incidence of consumers finding spiders is only one in
many thousands of boxes, when it happens it can be serious for the grower.
Depending on the kind of spider, a load can be returned, or a client grocery
may even switch to a competitor. Tolerance for spiders or webbing in grape
boxes is decreasing. Just a few years ago, spiders were rarely targeted for
chemical treatment. Today many growers are treating for spiders.
Some countries, namely Australia and New Zealand, prohibit imports
of grapes found to harbor live black widows, yellow sac spiders, and
jumping spiders in the genus Phidippus, because of their reputations as
biters. Grapes headed to these countries must first be gassed with CO2 and
SO2, and then inspected for any spiders or spider eggs. Any eggs found
must be verified dead or kept until hatching for identification by County
Agriculture Departments. The resulting shipping delays can be serious
problems for growers [4].
Spiders are pests only in table grapes. In the harvest of raisins and
juice grapes, spiders and their webs are separated from the grapes before the
product is packaged and sold. Spiders may still bother pickers, but not to a
level that would justify control with pesticides.
Some spiders are medical hazards because they bite. The black
widow is the only dangerous spider found in San Joaquin Valley vineyards,
but others may bite and cause minor symptoms such as mild to moderate
pain, redness, and swelling. Occasionally the symptoms are serious enough
to require medical attention. No local spiders seek out human victims, but
some bite more readily than others. Bites occur when spiders are trapped
beneath clothing or are otherwise cornered or brushed. Small spiders are
unable to cause significant bite-wounds.
Knowledge of spider bites is sketchy because the culprit spider is
often not captured or identified.
On the positive side, some spiders contribute to biological control of
pests. The impact of a spider species on vineyard pests depends on its diet,
its abundance, and a seasonal history which may or may not coincide with
that of the pests. Spiders are usually the most abundant group of large
predators in vineyards, typically more than 95%, excluding predators of
mites[8]. (Note: The collection methods in this study did not catch tiger flies,
which the authors separately estimated at about 5 per vine, making them by
far the most abundant predatory insect. See more information below).
Vineyards often have 10-50 spiders per vine [6] Some spiders are among
the most effective predators of leafhoppers, caterpillars, and other
pests[14][26][31].
The tolerance level for pests is higher in raisin and juice vineyards
than for table grapes, so biological control is more often considered
sufficient there. Thus the role of spiders in controlling pests becomes more
important than in typical table grape vineyards. Spiders are also a key to
pest management in organic table grape vineyards, where control options are
limited both for spiders as pests and for the pests they eat.
Most spiders are hyper-
predators; in addition to eating pests,
they also eat parasites and other
predators, including other spiders.
Thus they are both useful and
detrimental to pest management, with
the net contribution depending on the
species and on vineyard conditions.
One predator eaten by many
Tiger fly eating gnat. spiders is the tiger fly, Coenosia.
These small, grey flies rest on grape
leaves until they see something fly by, such as a leafhopper or small fly.
The tiger fly swoops out to catch the prey, then returns to a leaf, holding the
victim underneath, while they suck out the juice in about a half hour. Tiger
flies are very abundant in many vineyards, and significant predators of
leafhoppers.
Some small spiders and spiderlings eat many small parasitic wasps,
notably Aphidiidae, which are key control agents of aphids. However,
aphids are only rarely important pests of grapes.
Most spiders will eat other spiders, including their own species. The
impact of this hyper-predation on pest management depends on the relative
merits of the victorious vis-à-vis the vanquished spider.
When chemical control of spiders is necessary, the most effective
materials are the pyrethroids, with Danitol, Renounce, and Baythroid
registered in grapes, Lannate, and Lorsban. Lorsban may only be applied
before budbreak. Lorsban and pyrethroids have both contact and residual
action against spiders including black widows[16]. Lannate has good contact
activity, but little residual activity[16]. Unfortunately, all of these materials
are broad spectrum, and may disrupt natural enemies of other vineyard pests.
Indeed, killing spiders is detrimental to biological control.
Sprays should be applied before spiders build unsightly webbing on
bunches, but not so long before harvest that their populations have time to
reestablish to detrimental levels from neighboring blocks. Many species
hatch and balloon in the spring. Waiting until after this period will avoid
reinfestation. If possible, spray when eggs are not present, because eggs
tend to be protected from sprays. Smaller spider stages are easier to kill than
adults. For nocturnal species, night sprays are best. Timing should be
aimed at the species of spiders causing the most trouble.
Another consideration in timing is the presence of other pests which
can be controlled by the same sprays. For example, a pyrethroid spray will
also control leafhoppers or beetles, if timed correctly.
A four-page pamphlet published jointly by the U.C. Division of
Agriculture and Natural Resources and the California Agricultural
Technology Institute provides descriptions and photos of the most common
species, with notes on diet and habits[11]. The chief author, Michael
Costello, in collaboration with Kent Daane and others, has also published a
series of papers on spiders in San Joaquin Valley vineyards (see below).
The present article summarizes material from these and other studies,
and adds observations I have made in over twenty years of scouting grape
vineyards. I give my opinions about the relative importance of the spider
species as pests, biters, and predators, and give some suggestions about
control timing.
I have a number of biases in my spider observations. Most
observations are incidental to my monitoring of vineyard pests and their
natural enemies. I am rarely in the vineyards from October to mid-February,
so I do not have much direct evidence about late season or overwintering
habits. I have no night observations. There are months such as April-May
when I often look under bark, and others such as July when I rarely do. I am
more likely to notice feeding by a large spider than a small spider, and of
course I have more prey records for some web spiders than for wandering
spiders.
The spiders are discussed alphabetically by family. A family and
species index with links is included at the end of the paper.
Tables with the most important spider pests, biters, and pest control
agents are also included near the end.
Family Agelenidae
Funnel-web Weavers
Funnel-web weavers are moderately
large spiders that run on top of sheet-like
webs with tunnel retreat.
Hololena nedra
Most of the funnel-web weavers in our
area are Hololena nedra. They are abundant
in many vineyards unless treated.
Pest Status – HIGH Funnel web mess on grape bunch.
Funnel-web weavers are serious pests
because they cover bunches with thick, ugly webs. The webs are difficult to
remove, and often result in bunches being left on the vine. Pickers may be
wary of handling the infested bunches. Even when the webs are cleaned off,
the spider may remain inside the bunch and end up in the box.
Biting Risk – LOW
No bites are recorded, although the spiders are large enough to bite.
IPM Value – HIGH
Funnel-web weavers are important predators of leafhoppers, mainly
adults. Sometimes their webs contain many raisin moths or similar moths
(ID is difficult). Most other pests they eat are either minor pests or a
relatively small proportion of their diet.
Hyper-predation includes Aphidiidae and other parasitic wasps, tiger
flies, brown and green lacewings, minute pirate bugs (Orius), and some
predaceous beetles.
Hololena webs fill up with what is available. Near Eucalyptus trees
they eat many gum lerp psyllids. They often catch midges, gnats, and other
harmless Diptera. They also like ants.
I have 984 observations of prey in Hololena nedra webs:
Homoptera 64%
Leafhoppers 30% (293)
Psyllidae 33% (323)
Other 1%
(Aphids 9, Mealybugs 2)
Diptera 16% (Midges & gnats 84, small
flies 31, large muscoid flies 15,
Drosophila 15, Coenosia 9,
Therevidae 1, Bibionidae 1)
Hymenoptera 10% (Aphidiidae 57, ants Hololena nedra female.
28, Cynipidae 4, Pteromalidae 3,
Braconidae 1, small wasps 3)
Hemiptera 3% (False Chinch Bug 16, Orius 6, Lygus 1, other Miridae 1,
Reduviidae 1, Pentatomidae 1, other bugs 3)
Lepidoptera 3% (raisin moth & similar Pyralidae 26, cabbage looper 1, other
Noctuidae 4, other moths 3)
Thysanoptera 3% (thrips 33)
Neuroptera 2% (Brown lacewing 7,
Green lacewing 11)
Coleoptera 1% (Staphilinidae 2,
Carabidae 1, Nitidulidae 1,
Chrysomelidae bud beetle 1,
Anobiidae 1, small beetles 3)
Others (Psocoptera 3, Mayfly 1, Earwig
1, Termite adult 1)
Cluster of old egg sacs.
Pests 42% (leafhoppers, thrips, aphids, mealybugs, false chinch bugs, moths)
Predators and parasites 11% (tiger flies, rove beetles, minute pirate bugs,
brown and green lacewings, Aphidiidae and other small wasps)
Seasonal History and Habits
Adult females and large juveniles overwinter under bark.
Overwintering webs are usually built around the crotch of the vine. The
females lay eggs under bark in late winter or spring until mid-April, and
most are hatched by early May, but I have seen a few eggs as late as June 4.
The baby spiders make small webs on single leaves or attached to bark or
bunches. The webs increase in size and become unsightly on bunches
starting in July. New adults mature starting as early as September 22.
Control Timing
The best time to spray for funnel-web
weavers is after the eggs hatch but before the
webs cover the bunches. This would be the last
half of May to late June. Unfortunately, this
timing can be disruptive to biological control of
other pests, such as mealybugs.
Baby in leaf web. Fair control can also be achieved with a pre-
budbreak treatment with Lorsban or a pyrethroid.
Hololena tulareana
I found 1 male in a bunch of grapes in a vineyard south of Fresno, on
September 29. I suspect this and perhaps other Agelenidae are more
common than I know, because I typically assume they are H. nedra and
leave them alone, especially juveniles. Probably their diets and life histories
are similar to H. nedra.
Anyphaenidae
Ghost Spiders
Anyphaena pacifica
Hibana incursa (formerly Aysha incursa)
Ghost spiders look like sac spiders
with dark stripes on the sides of the
carapace. They are about the same size
and shape as Cheiracanthium. Their name
derives from their “ghostly” translucent
bodies.
Pest Status – MODERATE?
Ghost spiders are common in only a
few vineyards, but sometimes A. pacifica
is the most abundant spider [5]. I have not
seen them. They have habits similar to
Hibana incursa female.
Cheiracanthium, so they probably would
Photo © Ken R. Schneider
hide in bunches.
Biting Risk – LOW?
I have not found any records of bites by
ghost spiders. They are large enough to bite.
IPM Value – HIGH?
Ghost spiders are wandering hunters like
Cheiracanthium. They probably also eat similar
prey, such as leafhoppers, caterpillars, and other
spiders. In vineyards where they are abundant,
they may be important.
Anyphaena pacifica female
Hogg and Daane[18]. found that A. pacifica
Photo © Kyron Basu
suppressed leafhoppers on vines, but not as much
as Cheiracanthium.
Araneidae
Orb Weavers
Cyclosa turbinata
Trashline orbweaver
I have seen this tiny spider in only one
vineyard south of Kingsburg, which bordered
oak, stonefruit and riparian habitats. It has a
characteristic hump on the abdomen. The
spider builds its webs under the canopy. Prey
is retained in the web in a “trashline”.
The prey I observed was all very tiny
wasps and flies. The impact on IPM is trivial.
I have 15 observations from 2 webs:
Hymenoptera 67% (10 tiny parasitic wasps)
Diptera 33% (5 tiny flies)
I observed adult females from August
16 to September 13.
Cyclosa turbinata female with prey.
Photo © Victor Engel
Metepeira arizonica
Arizona Labyrinth Spider
Metepeira is moderate sized; much
smaller than Neoscona. The web is an orb in
front of a “labyrinth” resembling a cobweb,
with a tent-like nest in the middle, where the
spider hides and makes a string of leathery egg
sacs. This species is the dominant orb weaver
in many San Joaquin Valley citrus[3] and
pomegranate orchards. I found it in only a few
vineyards, but in some it is moderately
common.
Metepeira arizonica
juvenile resting in its nest.
Pest Status: LOW
The habit of hiding in a web nest keeps
the spiders and eggs out of bunches.
Biting Risk: LOW
Adults are moderate sized and not likely to bite.
IPM Value: LOW
I have not seen many pests in the webs. There is some hyper-
predation, but this spider is not abundant enough to make much impact.
Prey are retained in the web, but masticated so thoroughly that they
are often unrecognizable. Of those I identified, most were flies, but beetles,
wasps and ants were also present, with a few bugs and leafhoppers.
I have 32 observations in grapes:
Diptera 63% (Midges and gnats 16, Coenosia 1, Drosophila 1)
Coleoptera 13% (Collops 1, other 3)
Hymenoptera 16% (alate ant 1, bee 1, small wasps 3)
Hemiptera 6% (Orius 1, other 1)
Homoptera 3% (leafhopper 1)
Predators and parasites 16% (Coenosia, Collops, Orius, small wasps)
Pests 3% (leafhoppers)
Seasonal History and
Habits
I have seen
Metepeira females with
eggs as early as April
27, but most
observations were from
June 1 to September 23.
Eggs sacs are laid
Four eggsacs in a string. sequentially in a string,
and the eggs soon hatch.
This pattern suggests that the juvenile spiders overwinter.
Neoscona oaxacensis
Western Spotted Orbweaver
This may be the largest common
spider in San Joaquin Valley grapes. It is
by far the most common orb weaver. The
color pattern is highly variable, ranging
from orange to gray.
Pest Status: MODERATE
The web retreat is usually in a
curled leaf, but rarely the spider will hide in Neoscona oaxacensis female with
a space on the edge of a bunch. I once chevron pattern.
identified a carcass that was returned to a
grower from a grocery in Connecticut,
where a customer had complained.
Inspectors rarely find egg cocoons in
bunches. Fortunately, the cocoons are
loose, so the eggs are usually killed by
gassing[4].
Neoscona bothers workers when it
builds large webs across rows. Tractor
drivers commonly place large sticks in front
to break these webs.
Biting Risk: MODERATE
Neoscona oaxacensis male.
This spider is not aggressive. Bites
are rare, but sometimes occur if the spider is trapped under clothing.
Symptoms are minor, with initial stinging, and some redness and
swelling[35].
IPM Value: LOW
Neoscona is of little benefit in controlling grape pests. Small spiders
eat many thrips, but probably not enough to measurably impact the thrips
swarming at bloom time. They also eat some alate aphids and a few
leafhoppers.Larger spiders eat a few noctuid moths,
beetles, katydids, and bugs. Moths often
escape the webs, leaving behind scales[13].
The webs capture many alate aphids, but the
large spiders probably do not eat them.
Small spiders eat many parasites of
aphids (Aphidiidae). Larger spiders eat a few
predators, but most of these play only a minor
role in grape IPM. Tiger flies and lacewings A gray female.
are the most important.
I have 256 observations of prey in N. oaxacensis webs:
Thrips 33% (85)
Diptera 25% (large muscoid flies 30, gnats & midges 21,Tachinidae 4,
Syrphidae 4, Coenosia 3, Asilidae 1)
Hymenoptera 15% (Aphidiidae 19, Cynipidae 2, honey bee 2,
Ichneumonidae 1, Sphecidae 1, other 3)
Homoptera 14% (alate aphids 31, leafhoppers 2, psyllids 1)
Coleoptera 5% (sap beetle 2, click beetle 2, June beetle 1, lady beetle 1,
Notoxus 1, Dermestidae 1, Diabrotica 1, other small beetles 3)
Lepidoptera 4% (Noctuidae 5, alfalfa butterfly 1, small moths 2, medium
moth 1)
Hemiptera 3% (3) (Miridae 3, assassin bug 1, stink bug 1, Orius 1,
Coreidae? 1)
Other 2% (Katydid 2, green lacewing 2, praying mantis 1, psocid 1)
Predators 19% (Asilidae, tiger fly, Syrphidae,
Tachinidae, Notoxus, lady beetle, Sphecidae,
parasitic wasps, assassin bug, Orius,
Chrysopidae, Mantidae)
Pests 51% (thrips, aphids, click beetle, katydids,
moths, stink bug, leafhoppers)
Small juvenile in May.Seasonal History and Habits
Although N. oaxacensis has
only one generation in parts of its
range, such as San Diego[28], it has
two generations in the San Joaquin
Valley. It overwinters as eggs or
hatchlings in egg sacs[11]. The eggs
are protected in a loose silk cocoon.
Around the first week of April,
baby spiders are building small
webs on trellis wires and other
handy spots. First generation
spiders mature beginning the first
week of July, building webs
spanning the drive rows, with
Female in leaf tied together to resting nests protected by folded
protect her resting nest. leaves. The loose silk egg cocoons
can be found in similarly tied leaves
1-2 feet distant from the resting nests. The spiders remain active after laying
eggs, so I suspect that they lay multiple egg masses.
The second generation begins
hatching around the middle of July, and
matures much faster than the first
generation, presumably because of the
heat and perhaps better diet. It is not easy
to distinguish the first maturing females
of the second generation from the
surviving females of the first, but judging
by the progression of the instars, I believe
I found second generation females by the
first week of September, with their eggs
soon following.
Some eggs were still hatching in
late September. I don’t know when they Egg cocoon in folded leaf tip.
stop hatching and start hibernating. I saw
1 old egg nest at the base of a vine. Possibly the adults drop down to lay
overwintering eggs. Or perhaps eggs survive on leaves that have fallen in
the litter.Control Timing
The first generation can be controlled in May-June, which should be
sufficient for early-harvested table grapes. Late harvested grapes may be
better treated in August to avoid reinfestation by spiderlings ballooning in
from neighboring blocks.
Corinnidae
Ground Sac Spiders
& Antmimics
Meriola decepta
Ground sac spider
Meriola decepta looks similar to
Trachelas (see below), but is smaller and far
less common. The eggsacs are also smaller
versions of Trachelas. I have collected females
on vines from March 9 to May 10.
I have collected the male of another Meriola decepta female.
species, M. arcifera, from grape leaf litter but Photo © Rick Vetter.
not from the vine. The date was September 19.
Phrurotimpus mateonus
Antmimic
Phrurotimpus is a small fast-running spider that resembles an ant. It
is moderately common in some vineyards, but not enough to significantly
impact pests.
Right:
Phrurotimpus
mateonus female.
Photo © Rick
Vetter.
Left:
I think this is
the eggsac.The eggsac is probably a dome-shape with pink eggs, shown in the
photo, based on the appearance of the babies that emerged from a similar
eggsac. These eggs are usually found under bark, although the one in the
photo was on the surface of pistachio bark.
I have observed females March 29 and April 17, males April 6, and
eggs May 3 through May 25.
Trachelas pacificus
Ground Sac Spider
Trachelas has the same “sac spider”
shape as Cheiracanthium and was also
formerly in the Clubionidae. The carapace is
dark brown, and the abdomen gray.
Pest Status - MODERATE
T. pacificus occasionally lays eggs on
grape bunches, and inspectors have also
found adults in bunches [4]. They prefer to
hide under bark during the day when they are
not hunting. Trachelas pacificus female.
Photo © Lenny Vincent.
Biting Risk - MODERATE
This spider is known to bite.
Symptoms are similar to those of
Cheiracanthium, with mild to severe
local pain and red swelling.
Secondary infections sometimes
occur. This is possibly related to the
Trachelas pacificus male. habit this spider has of feeding on
Photo © Lenny Vincent. dead and decaying arthropods[30][34].
Vineyard workers are less likely to
encounter this spider than Cheiracanthium, because during the daytime it is
usually under the bark.IPM Value – HIGH
Trachelas may compete with
Cheiracanthium as a key predator of
leafhoppers and caterpillars. In some
vineyards it is the most abundant spider[5].
I have only one observation of predation in
vineyards, a leafhopper. Other researchers
list as prey leafhopper nymphs, mealybugs,
mites, OLR larvae, and Drosophila flies[11].
In citrus, I watched them eat thrips, mites,
insect eggs, and caterpillars[3].
Seasonal History and Habits
Trachelas is a nocturnal hunter, Egg sac on grape.
similar to Cheiracanthium, but in daytime
it usually hides under bark in flimsy nests. Juveniles and adults overwinter
under bark. Adults are found year around, with the lowest number in July[5].
Males are often found paired with a female. Females live longer than
Cheiracanthium, and may lay up to three egg sacs in a season[5]. Females
often guard the egg sacs under bark. I found eggs consistently from
February 23 to June 17 and from August 23 to October 1, but not in July.
Control Timing
A spray aimed at night from mid-June through July would probably
control Trachelas.
Dictynidae
Mesh-Web Weavers
Dictyna calcarata
Mallos pallidus
Dictynidae are small spiders with
large round abdomens. They have a
cribellum and their skin is covered with
flattened hairs. The web is a characteristic Mallos pallidus female with
interconnected mesh which may cover Aphidiidae prey on pomegranate
parts of the trunk or a grape bunch. leaf.Dictyna calcarata, the most common
species, has dark markings on the abdomen.
Mallos pallidus has lighter brown markings and
the carapace has a white peripheral stripe. Diet
and seasonal histories are similar, so I will treat
these two together.
Pest Status: LOW-MOD
Mesh-web weavers are too small to bother
most people. Very rarely, they will cover a bunch
with a flimsy mesh-web, with the spider and egg
sacs inside. The eggs could potentially delay
Dictyna calcarata shipments overseas, but inspectors so far have not
female on leaf nest. seen them. (Dennis Haines, pers. com.)
Biting Risk: NONE
All of our species are too small
to bite people.
IPM Value: LOW
Mesh-web weavers eat more
parasites and predators than pests.
Their webs are often found covering
infestations of homopteran pests such
Mesh web in pre-bloom bunch. as aphids,
mealybugs, and
soft scales. They eat the parasites that are attracted
to the homopterans. They also eat tiger flies as well
as many harmless dipterans.
It is not clear if the spiders are attracted to the
homopterans or vice versa, or both. The webs
probably provide some protection to the pests, and
the spiders eat the attracted parasites.
I have 111 observations of prey in mesh-webs.
Diptera 64% (gnats & midges 50, small flies 9,
Coenosia 4, Therevidae 4, Drosophila 4)
Hymenoptera
Small wasps 18% (Aphidiidae 13, Anagrus 4,
Pteromalidae 2, Braconidae 1) Mesh web covering a bunch.Ants 1% (1)
Psocoptera 5% (Psocidae 6)
Homoptera 5% (leafhopper adults 5)
Hemiptera 3% (false chinch bug 2, Lygus 1)
Coleoptera 2% (Staphilinidae 1, small beetle 1)
Neuroptera 2% (Brown lacewing 2)
Spiders 1% (Sassacus 1) Mallos female
with egg sac.
Pests 6% (leafhoppers, false chinch bug)
Hyper-predation 25% (parasitic wasps, tiger flies, rove beetle, brown
lacewing, spider)
On pomegranates I have web observations of many aphidiid, cynipid
and pteromalid wasps, and some aphids, dolichopodid flies, ants, and minute
pirate bugs.
Seasonal History and Habits
I have seen D. calcarata
adults from March 16 to August 26,
with eggs present most of that time.
It seems likely that adults are
present year around with multiple
generations. Probably adults and
juveniles and possible eggs
overwinter. M. pallidus is similar,
with adults observed at least April 8
to July 18. Mothers stay with their
egg sacs.
Mesh web covering vine trunks The mesh webs can be
may be communal spider colonies. anywhere on the vine, including
bark, leaves, and both early and late
bunches.
D. calcarata often lives in communal webs, with each spider
living territorially, but with its web connected by silk strands to its
neighbors. Some species of Mallos make similar communal webs[23]. This
is probably the case when mesh webs cover large sections of bark or most of
a grape bunch.Tivyna moaba
Tivyna moaba is an extremely tiny spider
likely to be overlooked by any but the most
dedicated spider hunters. They appear to live
only under bark where they build small webs and
lay their eggs. They are fairly quick and run to
hide when uncovered. In most cases I have
observed them near tiny ant species, such as thief
ants, Solenopsis molesta, which in turn were
Tivyna moaba female.
tending mealybugs. I have seen them eat such Photo © Rick Vetter.
tiny ants in captivity.
I have observed adult females from May 10 to July 7, with eggs most
of that time. Most likely the active period is longer than that. The eggsacs
are similar to D. calcarata but smaller and more gumdrop shaped.
Filistatidae
Crevice Weavers
Kukulcania geophila
Crevice weavers are sedentary
spiders a little larger than
Cheiracanthium. They have a
cribellum and their webs resemble
mesh-webs, but radiate outward from
holes in grape trunks or wooden end
posts. Females lack the external
genitalia called an epigynum found
Kukulcania geophila female. on typical spiders, so they can only
be distinguished by their size.
Pest Status – LOW
I observed one spider with its retreat between a grape bunch and the
trunk, but webs on the vine are almost always on the trunk with the spider in
a hole or under the bark.
Biting Risk - LOW
Crevice weavers are large enough to bite, but unlikely to come in
contact with workers. They are shy and stay under bark, even at night. I
know of no bite records.IPM Value: LOW
Diet is similar to black widows,
with many beetles, other walking insects,
pillbugs, and spiders. Pest prey are all
beetles, but the spiders are not common
enough to have a large impact. Hyper-
predation is about a third of the diet, but
the predators eaten are not key to
biocontrol of any important pests.
I have 55 observations of prey.
Crevice-weaver web on grape trunk.
Coleoptera 76% (Carabidae 16,
Tenebrionidae 10, bud beetle 6, Scarabaeidae 4, weevil 2, rootworm
beetle 1, Elateridae 1, other 2)
Diptera 15% (muscoid 5, Tipulidae 1, other 2)
Hymenoptera 11% (ant 6)
Isopoda 11% (pillbug 6)
Dermaptera 4% (earwig 2)
Spiders 2% (Trachelas 1)
Predators: 35% (Carabidae, earwig, spider)
Pests: 33% (darkling beetle, bud beetle, click beetle, rootworm beetle)
Seasonal History and Habits
Kukulcania females can live for
several years. They apparently all lay
eggs in synchrony in mid-June. Before
June 14 I have not seen any eggs; after that
all females had eggs, including four that
day and six more through July 5, plus one
August 5. Mothers hang onto their egg
sacs, which resemble big white duffle- Female with eggsac.
bags. I have seen males only in May, and
juveniles in March, April and August.Gnaphosidae
Ground Spiders
Nodocion eclecticus?
Nodocion voluntarius
Synaphosus syntheticus
Urozelotes rusticus
Zelotes nilicola
Several species of ground spiders
spend time under grape bark. The long
spinnerets are characteristic. They are
Nodocion voluntarius female.
not important pests, although inspectors
Photo © Rick Vetter
have occasionally found them in bunches
(Dennis Haines, pers. com.) They are not known to bite.
Ground spiders are nocturnal and I do not know if they hunt on the
canopy or only under the bark or on the ground, so I cannot say if they are
significant in pest management.
Gnaphosid species are hard to identify in the field, so many of my
observations are to family only. Nodocion voluntarius, the most common
species, is dark brown and a little smaller than Cheiracanthium. Urozelotes
rusticus is paler. Zelotes nilicola is a very small black species.
I have seen one juvenile eating a bark louse (Psocoptera), and another
eating a carpet beetle larva (Dermestidae), which can be a predator of
mealybug eggs. In captivity I
noted some gnaphosids apparently
eat ants.
Most of the gnaphosids seem
to overwinter as juveniles, with
adults present from early April to
as late as mid-July. This includes
at least N. voluntarius, U. rusticus
and Z. nilicola. I saw many
juveniles in February and March,
and again by mid-June. I found a
Urozelotes rusticus female. N. voluntarius female in a nest
Photo © Rick Vetter
with eggs on July 14.Linyphiidae
Dwarf Spiders
Erigone dentosa
Dwarf spiders are very common
in grass, leaf litter, and dirt. They are
very small, and all stages balloon, with
many landing on grapes. Most are
transient[20], but a few stay to build small
webs on leaves.
In grapes, I have seen Erigone
eating leafhopper nymphs, midges,
gnats, and a spider (E. dentosa). They
often locate in mite infestations and
probably eat many, but are not abundant Erigone dentosa male.
enough on leaves to have much impact Photo © Michael Costello.
on mite populations. They are also
common in flowering clusters, where they probably eat thrips.
I have only 12 observations in grapes:
Diptera 58% (midges & gnats 7)
Homoptera 33% (leafhoppers 4 nymphs)
Spider – 8% (E. dentosa 1)
In other crops I have seen them eat thrips, red and brown mites, soft
scale crawlers, and small moths.
I have seen adults from early March to late May.
Family Lycosidae
Wolf Spiders
Pardosa ramulosa
Schizocosa mccooki
Pardosa ramulosa is a small
wolf spider common on the ground[5].
In March juveniles often climb to the
tops of vines to launch themselves on
Pardosa ramulosa their ballooning trips. I have seen
juvenile on grape spur. females with eggs in March and
August, and a male in September.Schizocosa mccooki is a large wolf spider[5] which occasionally hides
under grape bark during the daytime. They are capable of biting, but not
likely to come into contact with workers.
Mimetidae
Pirate Spiders
Mimetus hesperus
Pirate spiders specialize in hunting web-building spiders, which they
lure by pretending to be prey. They are occasionally found in vineyards[7].
They are too small to inflict much of a bite.
Family Miturgidae
Prowling Spiders
Cheiracanthium inclusum
Cheiracanthium mildei
Yellow Sac Spiders
These moderate sized
yellow spiders wander the
canopy tapping their front legs
to find prey. They were
formerly classed in the
Clubionidae. C. inclusum is Cheiracanthium inclusum female.
also called the Agrarian sac Photo © Gayle Strickland.
spider, American yellow sac
spider or black-footed yellow sac spider.
C. inclusum is native to the Americas, but C. mildei is an introduced
European species[2]. In the 1990s Costello and others found only C.
inclusum in the San Joachin Valley[5] but C. mildei is more common now[20].
I also found more C. mildei. I will treat them together because they have
similar diets and life histories, and because many of my observations have
not distinguished between the two species.
Cheiracanthium can cross gaps between vines by using silk bridges it
constructs by allowing a breeze to pull silk out of the spinnerets until the line
attaches to something and sticks[29]. It shares this habit with the jumping
spider, Sassacus vitis and probably others.Pest Status - HIGH
Yellow sac spiders are among the most common spiders hiding in
bunches, and also like to lay eggs there in nests. They sometimes bite, so
they can be a nuisance to pickers. Because of their reputation as biters, they
are prohibited from imports to Australia and New Zealand, and the presence
of their eggs can delay shipments until they are verified as dead after
gassing[4].
Cheiracanthium nests and eggs are more common in raisin and wine
grapes than in table grape bunches. Table grapes typically get extra
insecticide sprays and have lower numbers of prey for spiders. The picking
and inspecting process also greatly reduces the incidence of these spiders in
packed grapes.
Biting Risk - HIGH
I suspect yellow sac spiders are responsible for the majority of spider
bites in vineyards. One researcher tells of picking grapes, finding several of
these spiders per bunch, and suffering multiple bites inside his shirt (Walt
Bentley, pers. comm.).
The bite is considered worse than most spiders, but is not in the same
league as black widow or brown recluse bites. Typical symptoms are a red
swelling between the size of a dime and a half dollar, often with multiple
small blisters filled with liquid, and strong itching (Dennis Haines, pers.
comm.). Some reports list mild to severe local or radiating pain lasting up to
12 hours or more. Occasionally muscle spasms or nausea may occur.
Necrosis is rare and slight, in spite of some claims in the literature [36].
Cheiracanthium species are also common in buildings, and cause
many of the spider bites inside and around homes [1][2].
IPM Value – HIGH
In my opinion, Cheiracanthium
species are the most effective spider
predators of pests in vineyards,
particularly of leafhoppers and
caterpillars. They are among the most
common spiders in vineyards, sometimes
the first[5].
Yellow sac spiders do not build a
hunting web, so it is difficult to
accumulate feeding observations. I have Juveniles in overwintering nests.
only 5, all leafhopper nymphs in oneobservation. Other vineyard researchers have observed them eating flies and
other spiders as well as leafhoppers[11].
Hogg and Daane[18] showed that in vineyard cages and laboratory
experiments, C. mildei greatly suppressed leafhopper numbers. It can also
suppress numbers and diversity of other spiders[18][19][21].
I monitor some raisin vineyards with a pattern of good leafhopper
control every year, where these spiders are very common, and they are the
most reasonable explanation for the diminution of leafhopper populations
each generation. These vineyards have almost no Anagrus egg parasites,
and not enough lacewings to control leafhoppers. I have rarely needed to
treat for leafhoppers in these vineyards.
I have also noticed that leafhopper
control in young vineyards with little
bark is often not as good as in older
vineyards. I suspect the reason is that
Cheiracanthium and similar spiders find
fewer hiding and overwintering places
when there is less bark.
Researchers in Israel found that C.
mildei is capable of controlling the
African cotton leafworm, Spodoptera
littoralis, in apple orchards[24]. I Daytime resting and molting nest.
consider it likely that yellow sac spiders
are key predators of omnivorous leafroller and other worms in grapes. In the
above mentioned vineyards I monitor, OLR is not a problem. We never
treat.
Yellow sac spiders probably eat other pests, such as thrips and mites,
but the role in control of leafhoppers and caterpillars seems most important.
Seasonal History and Habits
Females and larger juveniles overwinter under bark in heavy silk
nests. Females come out in spring and I have found them with eggs in nests
in folded leaves or under bark from late March through August. From June
onwards they also make egg nests in bunches. Inspectors sometimes find the
eggs in bunches boxed for shipping[4]. I have found relatively few females
and eggs in June and early July.
I have identified C. mildei adults every month from February to
September, with eggs starting in May. So far I have identified C. inclusum
adults only from March to May and July.In contrast to Peck and
Whitcomb[29] who report two eggsacs
following a single mating, Costello &
Daane [5] found that females die after
guarding one egg sac to hatching.
I found some juveniles still in
their overwintering nests until April
or even early May. They mature over
the summer and are presumably
responsible for the second peak of
eggs starting in July.
Hunting is usually at night.
During the day the spiders typically
hide in a flimsy silk nest built on a leaf Nursery nest in leaf unfolded to show
or under bark, or in a bunch. female with eggs.
An experienced observer can
recognize a good population of Cheiracanthium by looking for old nests on
leaves and under bark.
Control Timing
If control is deemed necessary, the best timing is probably at night in
June. Earlier timing may miss eggs or juvenile spiders still under the bark.
Oecobiidae
Flat-mesh Weavers
Oecobius navus
O. navus (formerly
called O. annulipes) is a
cosmopolitan species very
common in and on houses. In
Oecobius navus America they are called wall
female. spiders or baseboard spiders.
Europeans call them hackled-
band weavers, spiral spiders, or disk-net spiders.
Australians call them flat-mesh weavers, which I Eggs under silk nest.
think is the best name.Flat-mesh weavers are very small, and live within a nest-like web,
roughly star-shaped, with several entrances. In grapes they are typically
found on or under bark, but I saw one in a web on a leaf top.
Oecobius eats ants and gnats. In grapes, I saw them eat 3 ants and 2
gnats. In pomegranates, they ate 7 ants and 16 gnats. They are not
significant in pest management.
Adults are present year around. I saw eggs from March 31 to
September 20. I suspect this spider has multiple generations.
Oxyopidae
Lynx Spiders
Oxyopes scalaris
Oxyopes salticus
Lynx spiders are moderately common in many vineyards. They have
a characteristic tall carapace surrounded by eyes, and unlike most spiders,
they respond to motion nearby.
Pest Status: VERY LOW
I have never seen lynx spiders in
mature bunches. The eggs are laid before
picking season except for the earliest grape
varieties in July. Some are laid on the rachis
of early clusters.
Biting Risk: NONE
No bites are reported, and their
modest size makes biting unlikely.
IPM Value: LOW
Lynx spiders eat a few leafhoppers.
They love ants, but do not eat enough to
offer significant control. They also like
spiders and some other predators including Oxyopes scalaris
lady beetles, syrphid flies, and damsel bugs. eating a gray field ant.
They seem to have a small net negative
affect on pest management.
I have 17 prey observations in grapes:
Hymenoptera 35% (Ants 6)
Diptera 35% (Syrphidae 1, gnats & midges 4, muscoid 1)Spiders 23% (Erigone 2, Trachelas 1, Oxyopes 1)
Coleoptera 6% (lady beetle 1)
Pests: none observed.
Predators 35% (spiders, Syrphid fly, lady beetle).
Other observers have seen predation on leafhopper adults and small
[11]
wasps . On apple I saw one eat a damsel bug, Nabis.
Seasonal History and Habits
Lynx spiders build no hunting web. They are daytime hunters but
spend most of their time sitting still waiting for prey. Their eyes surround
their turret-like carapace, and they react quickly to nearby movement.
O. scalaris is much more common on vines. O. salticus prefers
ground vegetation[9].
O. scalaris apparently overwinters as juveniles, which I have seen
from March 3 to May 13. Adults were found from March 29 to July 13.
They are easy to see when shoots are small, but as the canopy fills in these
spiders are less evident. The female attaches her eggsac to a shoot or rachis,
usually well-hidden. I have only seen one, on the rachis of an early cluster
on June 11. Eggs must be present in May, because I have seen babies as
early as May 25. I have seen a few babies as late as September 2.
Judging by adult presence, it is possible that eggs could be laid during
harvest of early varieties in July, but the shape of a mature bunch does not
seem to offer a preferred oviposition site, except perhaps for the stem end.
O. salticus has a similar seasonal history.
Philodromidae
Running Crab Spiders
Tibellus chamberlini
Slender Crab Spider
This species has been collected from grapes, but rarely[5].Pholcidae
Cellar Spiders
Cellar spiders have very long legs, and are sometimes called “daddy-
long-legs spiders”. Their fangs are very small, incapable of biting people.
They are not common enough to impact pest populations much. They are
not significant pests, although they might hide in grape boxes.
The females have no external genitalia. They can be distinguished by
their size, and they carry their eggs.
Holocnemus pluchei
Marbled Cellar Spider
This immigrant from Europe is
our largest cellar spider. The webs
are inverted bowls, often with
retreats, and with characteristic little
white blobs. These spiders are very
common around houses and
occasionally seen in vineyards.
H. pluchei eats many Diptera
Holocnemis pluchei. and some ants, moths, and spiders.
They will eat moths of grape leaf
skeletonizers, which are rejected by some other spiders, such as funnel-web
weavers (Brian Carroll, pers. com.). In nectarines I have seen them eat a
katydid, a termite adult, and a fly.
I have 17 prey observations in grapes:
Diptera 82% (Drosophila 10, gnats 3, cranefly 3, fly 1)
Hymenoptera 12% (ant workers 3)
Lepidoptera 8% (possibly raisin moth 1, other 1)
Spider 4% (1)
Pests 8% (moths)
Predators 4% (spider)Psilochorus papago
Psilochorus utahensis
Psilochorus utahensis is smaller than H. pluchei and P. papago is
smaller yet. Psilochorus species build loose webs under grape bark or in
holes. They are common in irrigation pots.
All I have seen them eat is five ant workers, in grapes and peaches.
I have seen females with eggs June 29-
August 14, males from March 11 to May 11.
Most of these were probably the more
common P. utahensis.
Psilochorus papago male. Psilochorus utahensis female.
Photo © Rick Vetter.
Salticidae
Jumping Spiders
The Salticidae are the most diverse family of spiders in grape
vineyards. So far I have found 12 species, and 2 others are reported. The
salticid species composition varies widely between vineyards. Sassacus
vitis, the grapevine jumper, is common in almost all vineyards.
Most jumping spiders usually lay their eggs under bark. Some spend
most of their time under bark, some move between bark and canopy, and
some spend more time on the ground but occasionally visit the canopy.
Most Salticidae lay eggs inside flat nests occupied by the mothers.
Many species remain in the nest with the eggs. Otherwise the egg nests are
difficult to tell apart except by size.
Many of the Salticidae will bite if provoked, but the bite is not
serious. The larger species may cause some stinging pain and a red
swelling.Jumping spiders may be pests if they hide or lay eggs in bunches.
Phidippus species are forbidden by New Zealand and Australia.
Salticidae have at most a moderate impact on pest populations. Only
the grapevine jumper is abundant enough to eat much. Many species eat
fewer pests and more predators, including many other spiders.
Habronattus formosus
Habronattus hirsutus?
Habronattus pyrrithrix
Habronattus species spend much
of their time on the ground, where they
may be seen rapidly jumping around on
the dirt and short weeds, but they also
spend time on the canopy. They are
small for Salticidae. Females are drab
grey or brown, but males have some Habronattus pyrrithrix female
bright colors in frontal view.
I sometimes find Habronattus juveniles when I beat blooming clusters
for thrips. I saw a nymph eating a leafhopper, and an adult female in
captivity ate a tiger fly. These spiders are not common enough to have much
impact on pests.
I often have not distinguished
to species, especially with females.
Life histories are apparently similar
among the species. Adults are present
most of the season. I saw females
from April 6 to September 3, and all
months in between. Males I saw
from March 17 to July 19. I don’t
know where they lay eggs, but egg
nests in captivity are similar to other
Salticidae.
A grower reported a bite
between two fingers and showed me a
H. formosus female. There were no
Habronattus formosus female symptoms beyond the mild initial sting.Metacyrba taeniola
Metacyrba taeniola is almost
always under bark, although the
males may wander. It is small,
about the size of Sassacus, and the
egg nests are identical to that
species. This spider is common in
many vineyards.
Metacyrba taeniola female. My only prey record is a
small gnaphosid spider.
I saw females and eggs from late March to mid-August, skipping July
when I rarely look under bark.
Phidippus
These are the largest of our Salticidae, and brightly colored. They
sometimes bite and are forbidden by New Zealand and Australia. P. audax
and P. johnsoni adults are present early in the season, through June. P.
clarus and P. comatus are not as widespread and mature in July and later.
Inspectors occasionally find Phidippus eggs in bunches during
harvest. Based on seasonality, they are most likely to be P. clarus or P.
comatus. The other two species mature and lay their eggs earlier, apparently
no later than June. The eggs are far less common in bunches than Sassacus
eggs.
Phidippus audax
Bold Jumper
The bold jumper is our largest
Phidippus and the only one usually
without red markings except for young
juveniles. It is typically black with 3
abdominal spots, orange in large
juveniles and white in adults.
P. audax females and juveniles
are almost always found in their
massive silk nests under bark. The silk
is so thick that it is difficult to find any Phidippus audax female.
eggs or even to see the spider. It is The abdominal spots are
clear that they continually return to the orange on juveniles.
same nest through most of their livesand add more silk each day. Because of this habit, P. audax probably never
lays eggs in bunches, and is unlikely to hide there. Males often wander in
the canopy, but they also sometimes occupy the nest with the female.
Pest Status: MODERATE
P. audax is a pest only because it is forbidden in exports to Australia.
It is unlikely to be found in bunches, and the eggs are usually laid before
harvest season anyway.
Biting risk: MODERATE
Although I have no bite records, I have no doubt that the females
would bite if provoked. But workers are unlikely to encounter any but the
males, so the likelihood of a bite is low.
IPM value: LOW
Bold jumpers eat prey that crawl under bark, which does not include
many pests. The carcasses are often attached to the nest. Earwigs are a
favored food item. Oddly, earwigs appear to like to molt while attached to
these spider nests; some nests are covered with earwig shed skins. I have 17
food observations. All or most are predators.
Dermaptera 88% (Earwigs 15)
Coleoptera 6% (either Tenebrionidae or Carabidae 1)
Spiders 6% (Trachelas 1)
Life History
I have seen adult males and females from early March to mid-June. I
presume eggs are laid during that time. I suspect most overwinter as large
juveniles, which I saw from February through May 21.
Phidippus clarus
Costello and Daane [7][9] found fair numbers of P. clarus at the
Kearney Field Station in Parlier and in another vineyard near Reedley. So
far I have not seen this species. P. clarus occurs throughout the United
States.
Pest Status: MODERATE
A survey of photos on bugguide.net shows adults June through
September, which is later than P. audax and P. johnsoni, and places adults in
the harvest season. It occurs in only a few vineyards.Phidippus comatus
I have seen only two adult P.
comatus in grapes. Both were in nests
under bark with eggs, on April 4 and
September 8, but the later eggs looked
unhealthy. I have seen adults in
peaches, citrus, and on my house, from
July 17 to November. In these other
crops I saw many small juveniles in
April that were probably P. comatus or
P. clarus. This pattern suggests that
adult females and perhaps some eggs
overwinter. The adults are present
during harvest.
In peaches I saw one eating a Phidippus comatus female
smaller jumping spider.
Pest Status: LOW-MODERATE
I think this one is not common enough to be much of a threat.
Phidippus johnsoni
Johnson Jumper
P. johnsoni is bright red and black.
Workers are more likely to encounter this
species than other Phidippus, because it is
widespread and spends most daytime hours
hunting on the cordons or canopy. They
seem to make new resting nests every
night, rather than building on the same nest
like P. audax.
Pest Status – HIGH Phidippus johnsoni female.
Although harvest is probably too late The male has no black stripe
for adult P. johnsoni, the juveniles grow inside the red patch.
quickly and may reach large size by
August or September. They may hide in bunches, although of course they
will not lay eggs.Biting Risk – MODERATE
The Johnson jumper is considered a more aggressive biter than most
other spiders. Still, they would much rather flee than bite. It is far less
common than Cheiracanthium in vineyards. Symptoms are usually minor,
even less than Cheiracanthium. They include initial stinging pain and some
red swelling. (Russell 1970)
IPM Value – LOW
P. johnsoni does eat some leafhoppers, caterpillars, and moths, but it
is not common enough to have much impact on populations. It likes click
beetles.
Hyper-predation is a large part of the diet. P. johnsoni eats other
spiders, parasitic wasps, and probably tiger flies.
I have 8 prey observations of P. johnsoni:
Coleoptera 25% (click beetle 2)
Hymenoptera 25% (Aphidiidae 1, ant 1)
Hemiptera 13% (leafhopper 1)
Lepidoptera 13% (grape leaffolder 1)
Orthoptera 13% (cricket 1)
Spiders 13% (Sassacus 1)
Pests 50% (click beetle, leafhopper, leaffolder)
Parasites and predators 25% (spider, Aphidiidae)
Other observers have seen them eat flies and caterpillars in
vineyards[11]. In other habitats, they eat many flies and spiders, and some
mites, aphids, worms, moths, bees, ants, beetles, earwigs, and
harvestmen[3][22]. In captivity I saw them eat many Diptera including
Syrphidae, Muscidae, and Coenosia, and reject a katydid nymph and a small
darkling beetle.
Seasonal History and Habits
P. johnsoni overwinters as large juveniles[11] and maybe adults. I saw
adult females from February 24 to May 14, and medium to large sized
juveniles from March to late April and again in late July and August.
Unlike P. audax and P. comatus, P. johnsoni does not seem to stay
with its eggs for long. My associate Rob Weaver saw one in a moth trap
May 11, found eggs in a nest the next two weeks, and found them hatchedby June 1. I saw several egg nests from April 20 to May 5, probably this
species based on nest size and the adults seen in the vineyards. Babies
probably this species were present from early May to mid-June.
Control Timing
Probably June or July would be most effective, after most eggs are
hatched.
Platycryptus californicus
This flattened jumping spider is fairly large, close to Phidippus in
size. It is adapted to life under the bark. Most of my records are from
pomegranates, but in some vineyards it is fairly common.
The reclusive habits should keep it away from bunches, and the eggs
are laid before harvest season. It probably overwinters as juveniles, which I
saw from March 9 to May 10, and again August 23 and later. I saw females
throughout May to June 7, and eggs May 23-24.
I have only one prey record, an Oecobius spider in pomegranates.
Platycryptus is large enough to bite but I have no biting reports.
Workers are not likely to encounter them.
Platycryptus californicus female. With eggs in nest. Most salticids
have similar nests.Sassacus vitis
Grapevine Jumper
This small golden jumping spider is easily the most widespread and
common salticid in vineyards. It hunts in the canopy but lay eggs under the
bark or in bunches.
Sassacus is small enough that all stages can balloon. It can also travel
between vine rows on silk bridges, like Cheiracanthium.
Pest Status – MODERATE
Sassacus is too small to bother most
people. Unfortunately, it often lays eggs in
bunches, and the egg cocoon is tight enough to
protect the eggs from gassing. If inspectors
find eggs in grapes destined for Australia or
New Zealand, they are obliged to delay
shipment until the spiderlings hatch, allowing
positive identification[4]. This is not a
prohibited species, so after identification the
shipment can proceed. This delay, together Sassacus vitis eating midge.
with its abundance and proclivity for bunches,
gives this spider a high pest status.
Biting Risk – LOW
I have no biting records. I would like to say Sassacus is too small to
bite people, but it is about the size of Habronattus, which is guilty of at least
one little bite (see above).
IPM Value - MODERATE
Pests in the Sassacus diet include many thrips, a few aphids and an
occasional small caterpillar. It sometimes attacks leafhoppers but quickly
rejects them. I doubt if it has more than a minor impact on any of these
pests. About half of its diet is harmless Diptera.
Hyper-predation includes attacks on tiger flies and other spiders.
I have 29 observations of predation by S. vitis:
Diptera 41% (midges & gnats 7, Coenosia 2, Drosophila 1, small fly 1, large
fly 1)
Thysanoptera 21% (thrips 6)
Homoptera 7% (aphid 1, psocid 1)Lepidoptera 7% (armyworm caterpillars 2)
Spiders 10% (S. vitis 1, Salticidae 1, Trachelas 1)
Hymenoptera 3% (Aphidiidae 1)
Coleoptera 3% (Dermestidae larva 1)
Psocoptera 7% (Psyllidae 2)
Pests 31% (thrips, armyworms, aphids)
Predators and parasites 24% (spiders, Coenosia, Dermestidae, Aphidiidae)
Seasonal History and Habits
S. vitis juveniles and adults are present year around, and they both
overwinter under bark[5]. I saw eggs from early March to the end of June,
and in persimmons at the end of September. The presence of adults suggests
there may be eggs in July or August. There might be multiple generations.
Costello and Daane[5] found spring and late summer adult peaks.
Females often remain with the eggs in the nest, but not always. Most
egg nests are under bark, but they can also be found on clusters around
bloom time (late May) and in bunches at harvest time.
Control Timing
Probably within a month of harvest would be best, to avoid
reinfestation. June or July would knock down the population. Some will
always be hidden, but more will be exposed in a daytime spray.
Sitticus dorsatus
In the daytime, I found this tiny
jumping spider only under bark in nests.
These are baglike tents, not typical of
salticid nests . I do not know if Sitticus
hunts at night, but it seems unlikely since
Salticidae are visual hunters.
Sitticus dorsatus male. Females are brown.
Photo © Rick Vetter
Female in nest with eggs.So far I have only seen S. dorsatus in a couple of vineyards near
Parlier in Tulare County. I saw males April 1 to May 15, females May 15-
25 and August 6, and eggs May 15-25 and July 8.
Thiodina hespera
Thiodina hespera is common in
many valley habitats, such as citrus,
pomegranate, and persimmon. In grapes
they are usually scarce, but fairly
common in a few vineyards.
Pest Status – LOW MODERATE
Adults and eggs are either before
harvest or very late. Also not a very
common spider. Thiodina hespera female
eating a spider.
Biting Risk – MODERATE?
I have no biting records, but as a large salticid, I presume there is a
risk.
IPM Value – LOW
It is never very common, and
does not seem to eat a high proportion
of pests.
In citrus I have seen T. hespera
eating flies, midges, small wasps,
mites, and thrips [3]. In pomegranates
and persimmons I saw a couple eat a
fly and a small moth.
Life History and Habits
Juveniles overwinter. In all
Thiodina hespera male.
crops, I saw them March 17 to April
23 and September 1-24. I saw females May 4-31 and September 28, males
May 4 to June 18, and eggs on April 21 and September 28.
T. hespera spends the night hanging from a silk line in “suspended
bivouac”, so it can quickly drop if bothered by another spider[3].Metaphidippus chera
Metaphidippus manni
I occasionally see Metaphidippus
species in grapes, but more often in other
crops such as apple and almond.
Hogg et al. identified Metaphidippus
manni in the San Joaquin Valley, but much
fewer than near the coast[21]. My specimens
appear to be M. chera.
I saw females April 3-16 and July 1,
and eggs April 29 and July 1, in all crops.
Metaphidippus female.
Family Theridiidae
Cobweb Weavers
Cryptachaea porteri
These is a small cobweb weavers,
similar in size and shape to Theridion. The
pointed hump on the abdomen sets it apart.
They are common in some vineyards, but not
as widespread as Theridion. Until recently
the genus was Achaearanea.
Pest Status - MODERATE
Cryptachaea likes to attach its webs to
bunches, although the eggs are usually
hanging separate.
Biting Risk – LOW
They are too small to bite much.
Cryptachaea porteri female.You can also read
