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Pest Ants in Hawaii


Hawaii Ant Group (HAG)
The Hawaii Ant Group (HAG) is dedicated to the better understanding of ants (Hymenoptera: Formicidae) and their impacts in Hawaii.

AntWatch  NEW! 
AntWatch Hawaii is an educational, long-term effort to monitor the Hawaiian Islands for resident alien ant species and provide an early-warning network for newly introduced species. AntWatch relies on participating schools, teachers and students to collect geographic information on these introduced ant species. This information is transmitted to and analyzed by specialists in research management agencies. The AntWatch website "hosts all of the information you will need to learn more about ants in Hawaii, including ways to study and identify them, map their locations, and submit to data to experts with the tools to do something about them."
Change in Quarantine Action Policy for Ants Intercepted from Commodities Destined to the State of Hawaii  PDF icon   NEW!  (USDA, APHIS, PPQ, National Identification Services, April 10, 2002)
Red imported fire ant [RIFA] (Solenopsis invicta)
NOTE: The information on the red imported fire ant (Solenopsis invicta) that was formerly included on this page is now available at http://www.hear.org/AlienSpeciesInHawaii/species/solenopsis_invicta.
Little fire ant (Wasmannia auropunctata) distribution maps (Hawaii) - are now online! little fire ants on big island map

Ant Photos - available for public use

See also the ant key

Technomyrmex albipes


A pictorial key to the most pestiferous ant species threatening Hawaii's native fauna and flora

by Neil Reimer
U.S. Department of Agriculture, Plant Quarantine Branch, 701 Ilalo Street, Honolulu, HI 96813
voice: (808)       e-mail:

[Click here to view ant key]
Pictorial* ant key
 PDF icon 
(*Photos COMING SOON!)

A total of 44 ant species have been recorded in the Hawaiian Islands. None of these ants are native. They were all accidentally introduced by people. Ants have a devastating impact on the native fauna and flora. In the absence of ants, Hawaii's endemic fauna never evolved adaptations such as mimicry, or distasteful or appeasement secretions to thwart predation by ants, as is commonly observed with invertebrates from areas where ants are endemic. The establishment of ants over wide areas could result in the reduction and possible elimination of many native plant pollinators, threatening reproductive success. Certain ant species are also efficient seed predators.

Because of the severe impact ants can have on Hawaii's native fauna and flora, it is critical that native habitats be surveyed and monitored regularly for pestiferous ants so that adequate management strategies can be developed. It is important to determine the identity of the ant species present before an ant management program can be initiated, because ant behavior, biology, and ecology vary among species. Control strategies must be developed which are appropriate for the specific ant species. Ant Survey and Control Methods are provided in this key.

There are 16 ant species that are common or occasionally found in undeveloped habitats (non-urban and non-agricultural), and a few other ant species which are rarely encountered in undeveloped habitats. The ant species in this key are those that are most likely to cause a significant impact on Hawaii's native biota. Other species tend not to have a significant impact or are rarely encountered in undeveloped habitats.


How to use this guide

(A pocket magnifier of 5 to 20x magnification may be useful)

  1. Locate the worker ants. This key will not work for males or queens. Workers are wingless while males and queens have wings. Queens will lose their wings after they start a colony, but this stage is not commonly found outside the nest.

  2. Remember that worker ants of the same species can have different forms. Some may be larger than others or have larger heads. Make note if there are differences among workers. This will help separate different species and will be addressed in the guide.

  3. Begin at "Start" and compare the specimens with the captions and diagrams. There are two choices. Pick the appropriate diagram and follow the line to the next set of captions and photos.

  4. Check each subsequent choice carefully. There are at least two choices, but there may be more. Make sure that each line is followed to all captions.

  5. Continue until your specimen matches the captions and photo of a particular ant species.

CAUTION!  Keep in mind that this key only addresses the 16 most pestiferous ant species commonly found in undeveloped habitats. Remember that there are roughly 44 ant species in the islands.

If your ant specimen doesn't seem to fit the photo or caption and there are no other options, then you may have one of the few ant species that are rarely found in undeveloped habitats or you may have found a species new to Hawaii. Please help prevent a new pest outbreak by submitting specimens to Neil Reimer at the address below.

IF YOU NEED HELP TO IDENTIFY YOUR ANT SPECIMENS, CONTACT:

Neil Reimer, Department of Agriculture, Plant Quarantine Branch, 701 Ilalo Street, Honolulu, HI 96813
 voice: (808)       e-mail:

Ant Survey Techniques

The presence, density, and range of an ant infestation can be determined through various survey techniques. A number of techniques have been developed, including but not limited to the following: pitfall trapping, non-insecticidal bait stations, timed searching, and searching specific habitats. Often the technique which is most useful in finding the greatest number of species and their ranges is through simple visual searches of the habitat (Romero and Jaffe, 1989). This involves walking through the habitat and turning over stones and logs, etc. and looking for ants on the soil and leaf litter. The other techniques are more appropriate for determining ant and colony densities, foraging patterns, and other factors. If time and resources allow, then a combination of searching with pitfall trapping and/or placement of bait stations will be more rewarding.

Ant Control Methods

It is important to determine the identity of the ant species present before an ant management program can be initiated, because ant behavior, biology, and ecology vary among species. Control strategies must be developed which are appropriate for the specific ant species. Ants are easier to control when the colony is small and localized. Eradicating recent infestations is the best strategy.

 Some ant species (e.g. Hypoponera opaciceps) may be present but will never cause any significant problems to the environment, mainly due to the small colony size. No attempts at controlling this species will be needed. Other species can cause serious problems and should be controlled, such as the big-headed ant (Pheidole megacephala), Argentine ant (Linepithema humile), long-legged ant (Anoplolepis longipes), fire ant (Solenopsis geminata), Solenopsis papuana, and the black house ant (Ochetellus glaber). These ant species build large populations of interconnected colonies, occupy acres of land, and dominate the environment. Control of these ants is essential to prevent the decimation of the native fauna and flora.

 Control of ants in natural habitats is often difficult and problematic. Reasons for the difficulty in ant management in natural habitats include: 1) the terrain; 2) undesirable effects of ant control methods on non-target organisms; 3) abundance of naturally occurring food; and 4) changes in food preferences due to ant developmental stages.

The terrain.  Ants often occupy extensive areas of rough or inaccessible terrain. It may on occasion be difficult or impossible to gain access to these areas by foot. The result is that it can be quite expensive just to get to the infested area, let alone attempt to control the ants.

Undesirable effects of ant control methods on non-target organisms.

  Ant control methods could have equal or more severe deleterious effects on the native fauna in the area. Therefore, the use of a control method which is ant species specific is preferred. The use of insecticide-laden baits is ideal in these situations. Baits can be formulated to be attractive to ants, yet unattractive to the majority of native arthropod species. Under specific situations, baits can be offered in bait stations to minimize the impact on the native fauna. This is in contrast to other ant control techniques, such as insecticidal sprays, which are not host specific. Although sprays work well for ant control in some urban situations, they are not practical for naturalized areas because of non-target effects.

Abundance of naturally occurring food.

  The main difficulty with baits is that ant colonies often have a plentiful and varied diet available to them in natural areas, and the ants may not be interested in or attracted to the bait offered. Food preferences will change depending on which foods are naturally available in the environment. Naturally occurring food will change seasonally. For example, protein foods are less plentiful in the winter months, but more common in the spring and summer months when insect populations increase. Carbohydrate sources also are more plentiful when the vegetation is flowering (available as nectar), although certain ant species are known to tend Homopteran insects for the honeydew they produce year round.

Changes in food preferences due to ant developmental stages.

  Food preferences of ant colonies will also change due to ant developmental changes in the colony. For example, egg, brood (larvae and pupae), and worker production increases in Argentine ant (Linepithema humile) colonies in the spring months at Haleakala National Park (Krushelnycky and Reimer, unpublished). Increases in the production of eggs and worker ants will increase the protein requirements of the colony. During this time, baits with protein attractants are much preferred by this ant over carbohydrate or oil based baits. Later, the colonies shift to a preference for carbohydrate based foods in the late fall. At that time, the production of alates (winged reproductive forms of the ant) has ceased and the production of eggs and workers has decreased. The carbohydrates are still required, however, for the remaining workers in the colony.

Baits

  A number of baits are being developed which contain various attractants, but the majority of baits are directed towards the urban ant pests and a few agricultural pest species. In general, insecticide laden baits are the preferred method for management of pest ants in natural areas. They have the advantages of being easily applied over large, inaccessible areas, and being relatively host specific to the target ants. Different baits have different attractants so that they are attractive to specific ant species. For example, the bait Amdro contains soybean oil as an attractant and is readily fed upon by the big-headed ant (Pheidole megacephala). The granular baits Maxforce and Combat contain insect proteins as an attractant. These baits are attractive to Argentine ants (Linepithema humile). Both of these baits have been tested in natural areas and large agricultural acreage with various results. It is always a good idea to test a small amount of the bait to test whether the ants will carry it back to the nest, before committing to a large-area control program.

  • Amdro

      Amdro has proven to be very effective against the big-headed ant (Pheidole megacephala) in abandoned pineapple fields. Applications at 1.5 pounds/acre has given 100% control. Although no trials of this bait have been conducted in forested areas, it would seem to be a excellent candidate for testing. The abandoned pineapple fields contained an abundance of alternative food sources, yet Amdro was readily accepted by the ants.

  • Maxforce

      Trials at Haleakala National Park have demonstrated the effectiveness of Maxforce against the Argentine ant (Linepithema humile). Although 100% ant control was not achieved when Maxforce was applied at the rate of 2 pounds/acre in native scrubland at 6500 feet, the ants were reduced significantly. Typically, a reduction in ant numbers of 80-95% was observed within one week after treatment. The numbers of ants remained low at 70 to 89% below pretreatment levels two months after treatment. Maxforce may have greater effectiveness if applied at a time when the ants are at a peak in their acceptance of protein food sources. Maxforce should work very well at managing small localized ant populations. Maxforce may also be effective in maintaining a buffer zone to prevent ant movement into areas particularly sensitive to ant invasion.

References

Romero, Hernan, and Klaus Jaffe. 1989. A comparison of methods for sampling ants (Hymenoptera: Formicidae) in savannas. Biotropica 21(4): 348-352. 

References

Medeiros, A. C., L. L. Loope, and F. R. Cole. 1986. Distribution of ants and their effects on endemic biota of Haleakala and Hawaii Volcanoes National Parks: a preliminary assessment. Proceedings of the Sixth Conference in Natural Sciences, Hawaii Volcanoes National Park. Cooperative National Park Resources Studies Unit, Department of Botany, University of Hawaii, Honolulu, Hawaii, USA. 

Perkins, R. C. L. 1913. Introduction. Fauna Hawaiiensis 1(6): i-ccxxvii(xli-xlii).

Romero, Hernan, and Klaus Jaffe. 1989. A comparison of methods for sampling ants (Hymenoptera: Formicidae) in savannas. Biotropica 21(4): 348-352.


Ants of Importance to Hawaii Land Managers

Description of key characters for ID

Anoplolepis longipes (Jerdon) [long-legged ant]

Color: reddish

Size: 1/4"

Nodes One (node=segment between thorax and abdomen)

Other Characters: long legs and antennae; slim body;

Behavior: individuals are fast moving;

Colonies: are large (>200 workers, many queens) and interconnected;

Nest: in rock piles and rock walls;

Habitat: found in dry, mesic, and wet areas below 3,000 ft. elevation;

Foraging Behavoir: workers forage by spreading over foraging area, rarely form trails except up trees or over narrow passages;

 

 

Camponotus variegatus (Fr. Smith) [carpenter ant]

Color: reddish to light brown

Size: 1/2"; some workers with larger heads than others;

Nodes: one

Other characters: largest ant species in the islands;

Behavior:

Colonies: often small (20 to 200 individuals, many queens);

Nest: nest in wood, under logs, or under or in any undisturbed, dry covering;

Habitat: found throughout the islands in most habitats;

Foraging Behavoir: workers forage singly, never form trails unless moving young;

 

 

Cardiocondyla venustula Wheeler

Color: brown to black

Size: 1/8"; all one size

Nodes: two

Other characters:

Behavior:

Colonies: often small (20 to 200 individuals, many queens);

Nest: under rocks and debris

Habitat: found from 0 to 10,000 feet elevation in dry, mesic and wet climates

Foraging Behavoir: single foragers, don't form trails

 

Hypoponera opaciceps (Mayr)

Color: black

Size: 1/8"

Nodes: one

Other characters:

Behavior: fairly slow movers,

Colonies: small (<50 workers, one queen)

Nest: in soil, decaying wood, under stones

Habitat: most commonly in mesic to wet areas above 2,000 feet;

Foraging Behavoir: single foragers, no trails

 

 

Linepithema humile (Mayr) [Argentine ant]

Color: brown

Size: 1/8"

Nodes: one

Other characters:

Behavior:

Colonies: large (>100 workers, many queens), interconnected to other colonies

Nest: under stones

Habitat: found from 0 to 10,000 feet, more commonly above 3,500 feet in dry or mesic habitats

Foraging Behavoir: single foragers but also form trails to food and between nests

 

 

Monomorium floricola (Jerdon)

Color: bicolored, head and abdomen dark brown, thorax lighter brown to yellow;

Size: 1/16"

Nodes: two

Other characters: very small and thin;

Behavior: will sting

Colonies: large (>100 workers, many queens)

Nest: in twigs and branches and under bark of trees and shrubs

Habitat: dry and mesic areas below 3,000 feet

Foraging Behavoir: form trails along ground and in trees

 

 

Ochetellus glaber (Mayr) [glaber ant]

Color: black

Size: 1/8"

Nodes: one

Other characters:

Behavior: will bite; feeds on honeydew from aphids and mealybugs

Colonies: large (>100 workers, many queen), interconnected

Nest: in soil, under logs and rocks

Habitat: dryer areas below 3,000 feet

Foraging Behavoir: workers form trails

 

 

Paratrechina bourbonica (Forel) [crazy ant]

Paratrechina longicornis (Latreille) [crazy ant]

Color: black for P. bourbonica, black with purple irridescence for P. longicornis

Size: 1/8"

Nodes: one

Other characters: long legs and antennae for P. longicornis; more robust for P. bourbonica

Behavior: fast runner, especially when disturbed; feeds on honeydew

Colonies: large (>200 workers, one queen)

Nest: in soil under stones and debris

Habitat: dry areas below 3,000 feet

Foraging Behavoir: forms trails

 

 

Pheidole megacephala (Fabricius) [big-headed ant]

Color: brown

Size: 1/8"; some workers with large heads

Nodes: two

Other characters:

Behavior:

Colonies: large (>200 workers, many queens)

Nest: in soil, sometime with donut of dirt around hole

Habitat: found in dry and mesic areas below 3,000 feet;

Foraging Behavoir: workers forage by spreading over foraging area but will forms trails up trees and to food sources

 

 

Plagiolepis alluaudi Forel [little yellow ant]

Color: yellow

Size: 1/16"

Nodes: one

Other characters:

Behavior: tends insects for honeydew

Colonies: large (>50 workers, many queens)

Nest: in trees

Habitat: dry and mesic areas below 3,000 feet

Foraging Behavoir: forms trails

 

 

Solenopsis geminata (Fabricius) [fire ant]

Color: red

Size: 1/8"; workers range in size from less than 1/8" to about 1/4"; some with large heads

Nodes: two

Other characters:

Behavior: will sting aggressively; tends insects for honeydew

Colonies: large (>200, many queens)

Nest: in soil often with piles of dirt around entrance

Habitat: dry areas below 1,000 feet, in leeward areas of islands

Foraging Behavoir: workers forage by spreading over foraging area, will form trails

 

 

Solenopsis papuana Emery

Color: black

Size: 1/16", all workers of same size

Nodes: two

Other characters: antennae with 2 segmented club

Behavior:

Colonies: large (>1000 workers, many queens)

Nest: in soil under rocks, most often associated with rotting wood in or near soil

Habitat: found mainly in mesic and wet forested areas between 1,000 and 3,500 feet

Foraging Behavoir: form trails but workers also forage by spreading over foraging area

 

 

Tapinoma melanocephalum (Fabricius) [tiny yellow house ant]

Color: bicolored, black head with yellow abdomen and thorax

Size: 1/16"; all workers of same size

Nodes: one but appears as none

Other characters:

Behavior: very fast mover

Colonies: large (>200 workers, many queens)

Nest: under rocks

Habitat: found in dry and mesic areas below 2,000 feet

Foraging Behavoir: forms trails

 

 

Technomyrmex albipes (Fr. Smith)

Color: brown to black with white feet (not easily seen)

Size: 1/8"

Nodes: one but may appear as none

Other characters:

Behavior: tend insects for honeydew

Colonies: small or large (>200 workers, many queens)

Nest: in trees

Habitat: found in dry, mesic, and wet areas below 5,000 feet

Foraging Behavoir: form trails

 

 

Tetramorium simillimum (Fr. Smith)

Color: brown; sometimes abdomen appears dark brown and head and thorax are light brown

Size: 1/8"

Nodes: two

Other characters:

Behavior:

Colonies: large (>100 workers, many queens)

Nest: in soil

Habitat: found most commonly in dry lowland areas

Foraging Behavoir: forms trails


Other links RE: pest ants in Hawaii

Other links RE: pest ants in Hawaii (from the Hawaiian Ecosystems at Risk (HEAR) project):


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This page was created by the Hawaiian Ecosystems at Risk project (HEAR) on 23 April 1997, and was last updated on 08 July 2004 by PT. Questions, commments, or suggestions RE: this page? E-mail the webmaster!