WORLD'S WORST INSECT INVADERS: ANTS, BEES & WASPS - Invasive Species Council
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Invasive Insects: Risks and Pathways Project
WORLD’S WORST
INSECT INVADERS:
ANTS, BEES & WASPS
T
UPDATED: APRIL 2020
he Invasive Insects: Risks and
Pathways project has found that the
world’s environmentally harmful
invasive insect species are dominated by
just one insect order – that of ants, bees
and wasps (Hymenoptera)1. This order
accounts for 16 of the 17 insect invaders
known to be causing environmental
harm in Australia. Why are ants, bees and
wasps so successful and so harmful?
One answer is that they are habitual and
versatile world travellers. Of the dozen
main pathways by which invasive insects
reach new countries, Hymenoptera use
them all and frequently so1.
Another clue is that most invasive
Hymenoptera are social, and the most Western yellowjackets, invasive in Hawaii, are aggressive hunters.
harmful of them – typically ants – tend Photo: TJ Gehling | Flickr CC BY-NC-ND 2.0
to live in extremely large societies, which
most other animals from their invasive
can be more populous than the biggest
range2,3. The ants benefit enormously by
human megapolises.
‘farming’ an invasive scale insect from
which they gain honeydew. They have
DOMINANT INSECT killed tens of millions of red land crabs by
INVADERS spraying their eyes and mouthparts with
formic acid. Because the crabs eat leaf
Of the world’s 24 insect orders, the litter, seeds and seedlings, their absence
Hymenoptera accounts for half the has drastically altered the structure and
species in the assessment pool of the In their invasive range, European fire ants composition of invaded forests, and the
Invasive Insects: Risks and Pathways reach extremely high densities, displacing forest canopy is suffering dieback due
project (made up of species for which nearly all other ants. to the outbreaks of invasive scale insects
there is evidence of environmental harm Photo: Ryszard | Flickr | CC BY-NC 2 protected by the crazy ants and from
somewhere in the world)1. The leading sooty mould caused by honeydew4. The
invaders are ants (all social), accounting loss of crabs also enables the spread of
for more than one in eight species another invasive species, the giant African
national eradication of red imported fire
assessed – three times as many as any land snail5.
other insect family. Bees, most of which ants, electric ants and browsing ants, and
are social, and parasitoid wasps, which partial eradication of yellow crazy ants
are not, are also common invaders. (Wet Tropics) and Argentine ants (Norfolk WHAT WE MUST KEEP
Of Australia’s 17 insect invaders known to
Island).
OUT OF AUSTRALIA
be causing environmental harm, 16 are The impacts of social hymenopteran Of the 27 social hymenopteran species
Hymenoptera (9 ants, 3 wasps, 3 bees) species are complex, brought about assessed so far in the Invasive Insects:
and 1 is a beetle (Table 1)1. Three have mainly by predation, competition, and Risks and Pathways project, 24 have been
been recorded in Australia for the first interaction with other exotic species1. rated as ‘of concern’ or ‘of substantial
time just this century. As one indicator of Yellow crazy ants on Christmas Island concern’ (15 ants, 5 wasps, 4 bees)1. Of
the harm caused by social hymenopteran demonstrate all these mechanisms. these, more than half (7 ants, 3 bees
species, Australia is currently spending Capable of achieving extremely high and 3 wasps) are already established in
over $60 million a year on eradication population densities (more than 2000 a Australia. It is important to stop more
programs for five ant species – seeking square metre), they aggressively displace introductions of these species – to
INVASION WATCH: Ants, bees & wasps
Table 1: Invasive insect species for which there is evidence of environmental harm in Australia
Order Family Species Common name Date of first detection First state or territory
or mention record
Hymenoptera Apidae Apis mellifera European honey bee 1820 Queensland
Hymenoptera Formicidae Solenopsis geminata Tropical fire ant 1863 ?
Paratrechina
Hymenoptera Formicidae Black crazy ant 1886 Queensland
longicornis
Hymenoptera Formicidae Monomorium floricola Floral ant 1910 Queensland
Monomorium
Hymenoptera Formicidae Singapore ant 1910 Queensland
destructor
Hymenoptera Formicidae Pheidole megacephala African big-headed ant 1911 Queensland
Coleoptera Scarabaeidae Heteronychus arator African black beetle 1920 South Australia
Hymenoptera Formicidae Linepithema humile Argentine ant 1939 Victoria
Hymenoptera Vespidae Vespula vulgaris Common wasp 1959 Victoria
Hymenoptera Vespidae Vespula germanica European wasp 1959 Tasmania
Hymenoptera Formicidae Anoplolepis gracilipes Yellow crazy ant 1975 Northern Territory
Hymenoptera Vespidae Polistes chinensis Asian paper wasp 1979 New South Wales
Hymenoptera Megachilinae Megachile rotundata Leafcutting bee 1987 New South Wales
Hymenoptera Apidae Bombus terrestris Large earth bumblebee 1992 Tasmania
Hymenoptera Formicidae Solenopsis invicta Red imported fire ant 2001 Queensland
Wasmannia
Hymenoptera Formicidae Electric ant 2006 Queensland
auropunctata
Hymenoptera Apidae Apis cerana Asian honey bee 2007 Queensland
prevent re-invasion of those being
eradicated and new areas being invaded, Table 2: The invasive social Hymenoptera not established in
and to stop new genetic material from Australia that are of concern or substantial concern due to
boosting their invasiveness. This leaves environmental impacts elsewhere in the world
at least 11 additional species that are
likely to be a high priority to keep out of Family Species Common name
Australia (subject to Australia-specific risk
assessment), including 8 ants, Apidae
Apis mellifera
East African lowland honey bee
2 wasps and 1 bee (see Table 2). There scutellata
are likely to be other priority species
Formicidae Myrmica rubra European fire ant
once 28 additional Hymenoptera in the
assessment pool have been assessed. Formicidae Pachycondyla chinensis Asian needle ant
WHY ANTS ARE SUCH Formicidae Paratrechina fulva tawny crazy ant
SUCCESSFUL INVADERS Formicidae Solenopsis richteri black imported fire ant
The Hymenoptera is one of, if not the
largest of, insect orders, abundant Formicidae Technomyrmex albipes white-footed ant
everywhere except in polar regions Formicidae Lasius neglectus invasive garden ant
and ecologically highly influential. A
major reason for their success is the Tapinoma
Formicidae ghost ant
melanocephalum
nutritious food they provide to their
offspring6. Parental care in this order Formicidae Solenopsis papuana Papuan thief ant
has been taken to a new level with
the evolution of sociality, which has Vespidae Vespula pensylvanica western yellowjacket
occurred several times, being the case Vespidae Vespa velutina Asian hornet
for some bee and vespid wasp species
and for all ants. Social structures enable
The most successful invasive attended by her sterile daughters, who
dozens to millions of individuals to work
Hymenoptera are the ants – which aggressively defend their territory,
cooperatively to exploit resources, build
achieve an extreme form of sociality. particularly against members of their
nests, care for young, and maintain
A typical ant colony has one queen own species7. But many invasive ants
strong defences.
INVASION WATCH: Ants, bees & wasps
Coleoptera Dermaptera Diptera Hemiptera Hymenoptera Isoptera Lepidoptera Thysanptera
Biological
control
Contaminant
nursery material
Food
contaminant
Contaminant on
plants
Timber trade
Transportation of
habitat material
Container/bulk
Hitchhikers on
ship/boat
People and their
luggage
Vehicles
Organic packing
material
Natural dispersal
across borders
Figure 1: The use of introduction pathways by invasive insect orders. Only the most prevalent pathways and insect orders are shown. Circles and their sizes represent
the relative contribution (%) of each insect order to the number of species using a particular pathway. Circle sizes (from smallest to largest) represent 1-10%, 11-20%,
21-30%, 31-40%, 41-50%, 51-60%.
form supercolonies, with many queens a few years, probably due to competition with other species7, 8. Extremely high
and many interconnected nests. The with other supercolonies and other ant densities can be achieved, allowing
individuals from different nests behave ant species9. But their supercolonies in domination over other species. Over 1
amicably rather than aggressively towards invaded areas can cover hundreds of million Argentine ant queens and 4.4
each other and can move freely between kilometres, and some are more than cubic metres of workers and brood were
nests. ‘Thus, the cooperation that a century old. One colony along the captured from one 8-hectare orchard in
promotes the success of social insects Mediterranean coast extends more the United States (cited in 10).
generally appears to be exaggerated in than 6000 km, and one in Australia
Ants also have flexible diets (as
many invasive ants’8. spans 2800 km9. These and several
omnivores), easy-to-fulfil nesting
other supercolonies have their origins
The largest known supercolonies are requirements, and an association with
in just one ancestral supercolony from
those of the Argentine ant (Linepithema humans that allows them to travel around
Argentina, and represent ‘the most
humile). In its native range, it usually the world in traded products and as
populous known animal society’10.
forms colonies with small territories that stowaways on ships. The Invasive Insects
are aggressively defended against other Normally, low genetic diversity is thought Risks and Pathways project found they
Argentine ants, and lives among many to be harmful but, for ants, by reducing travel frequently on all 10 of the most
other native ant species8. Sometimes it their aggression towards their own kind, prevalent unintentional pathways for
forms supercolonies spanning hundreds it frees up a lot of extra energy for colony insect introductions (see Figure 1).
of metres, although these endure for only growth, foraging, defence and competing
INVASION WATCH: Ants, bees & waspsAsian needle ant. Photo: © Matt Bertone
IMPLICATIONS FOR Recommendation 3 density and biomass. Insectes Soc. 52: 266–273.
BIOSECURITY As a high biosecurity priority, reduce
4. O’Dowd DJ, Green PT, Lake PS (2003):
Invasional ‘meltdown’on an oceanic island.
The prevalence and harmfulness of the risks of unintentional introduction Ecology Letters. 6: 812–817.
the invasive hymenopteran species, pathways for the Hymenoptera. Given 5. Green PT, O’Dowd DJ, Abbott KL, Jeffery
particularly ants, means they should be their flexible travel habits – with ants M, Retallick K, Mac Nally R (2011): Invasional
a top biosecurity priority in Australia. As in particular common on all 10 of the meltdown: invader–invader mutualism facilitates
tiny, tough and versatile travellers, they most prevalent unintentional pathways a secondary invasion. Ecology. 92: 1758–1768.
are also very challenging for biosecurity. worldwide for invasive insects – the only 6. Quicke DLJ (2009): Chapter 127 -
We must strive to prevent new feasible way to prevent new invasive Hymenoptera: Ants, Bees, Wasps. In: Resh
introductions, including of the species hymenopteran species is to reduce the VH, Cardé RT, editors. Encyclopedia of Insects
already here, eradicate those we can, and frequency by which they travel with (Second Edition). San Diego: Academic Press, pp
protect Australian biodiversity from their traded products and as stowaways on 473–484.
impacts. ships and planes. This requires assessing 7. Holway, Suárez ML, Case T (1998): Loss of
the risks of each of these pathways, intraspecific aggression in the success of a
imposing import conditions to reduce widespread invasive social insect. Science. 282:
Recommendation 1 949–952.
the risks and improving inspection and
Fully implement Australia’s invasive diagnostic protocols. 8. Tsutsui ND, Suarez AV (2003): The colony
ant biosecurity plan11. This plan was structure and population biology of invasive
adopted in mid 2019 by all national, state Recommendation 4 ants. Conservation Biology. 17: 48–58.
and territory governments but has no 9. Vogel V, Pedersen JS, D’Ettorre P, Lehmann L,
targeted funding for implementation. As a high biosecurity priority, improve Keller L (2009): Dynamics and genetic structure
One particularly important action, Australia’s preparedness to respond to of Argentine ant supercolonies in their native
essential for coordination and motivation, incursions of social Hymenoptera. This range. Evolution. 63: 1627–1639.
is to establish a ‘permanent national requires developing effective surveillance 10. Van Wilgenburg E, Torres CW, Tsutsui ND
body to coordinate national actions on programs and being ready to efficiently (2010): The global expansion of a single ant
invasive ants.’ This is consistent with the eradicate new incursions. Hymenopteran supercolony. Evolutionary Applications. 3:
seriousness of both existing and potential surveillance in Australia can be boosted 136–143.
threats to the Australian environment, as by supporting citizen science programs. 11. Department of the Environment and Energy
well as human amenity and the economy. (2018): Draft National Invasive Ant Biosecurity
SOURCES
Plan 2018-2028. Australian Government.
Recommendation 2 1. Invasive Insects Risks and Pathways project
Develop a biosecurity plan (or plans) unpublished data (2019): Monash University and ABOUT THIS PROJECT
for other social Hymenoptera. With the Invasive Species Council. The Invasive Insects: Risks and
potential for invasive bees and wasps to 2. Abbott KL, Green PT (2005): Collapse of an Pathways Project is a partnership
ant–scale mutualism in a rainforest on Christmas between Monash University and the Invasive
disrupt pollination communities, and the
Island. Oikos. 116(7): 1238-1246. Species Council. To find out more visit
predatory efficiency of invasive wasps, invasives.org.au/risks-and-pathways.
they can have profound ecological 3. Abbott KL (2005): Supercolonies of the
impacts. invasive yellow crazy ant, Anoplolepis gracilipes,
on an oceanic island: Forager activity patterns,
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