Trap-jaw Ant, Vol. 7, No. 27
Odontomachus haematodus
Order: Hymenoptera
Family: Formicidae
“We’ve got these big jumping ants in the yard and they sting!”
Trap-jaw ants are unusual ants—in so many ways. These are big ants, with workers that are over 1/3 inches long, and they walk about with their large mandibles cocked open like a bear trap. When they encounter prey or even some inanimate object, the mandibles spring closed at one of the fastest speeds in nature. If it is a prey item, such as a small insect that triggers the trap, they’ve got it. If it is an inanimate object, like a stick, the force of the closing jaws may propel the ant backwards several inches, causing it to appear to jump. This jumping action is thought to help these ants escape from larger predators or from other dangers, such an antlion pit. (See Bug's Eye View No. 2 of 2018 for a brief article on antlions. Though trap jaw ants are probably a bit too big for antlions to subdue.
Trap-jaw ants nest in decaying wood and leaf litter, where they are sometimes encountered by gardeners as they work in the yard. These big ants are quick to sting in defense of their nest, and the sting is often described as being a bit more painful than a honeybee sting. Like fire ants, trap-jaw ants often grasp the skin with their mandibles and sting several times. The sting is smooth, no barbs, and can be used repeatedly.
Another strange thing about these ants is their unusually long antennae. But then they need to be long to reach beyond those big mandibles. Stranger still, young trap-jaw ant larvae have special sticky pads on their back that allow workers to hang them from the ceiling of the brood galleries. That’s a novel way of keeping the young ones from being underfoot!
Fortunately, trap-jaw ant colonies are usually small, consisting of a few hundred workers, and they are not common here in Mississippi. So far, trap-jaw ants only occur in Jackson County (Pascagoula area) and parts of Green County. This makes sense because these non-native ants were first found in Mobile in 1956. Now they are well-established in Mobile, parts of Florida, and the New Orleans area, as well as these two counties in Mississippi. If you detect what you think may be trap-jaw ants in other areas of the state, please let us know.
This short video of trap-jaw ants in action was filmed by Joe MacGown, Ant Taxonomy Specialist with the Mississippi Entomological Museum. Notice how they use their long antennae to detect and orient to what they perceive as an intruder in their nest area and attack it with their mandibles. Also notice the force with which some of the ants are propelled backward by those snapping mandibles.
Control: Eliminate trap-jaw ant colonies by spraying nest sites and surrounding area with a pyrethroid insecticide such as bifenthrin + zeta-cypermethrin, gamma-cyhalothrin, cyfluthrin or permethrin. Ready-to-use hose-end sprays are a convenient and effective way to apply such treatments, but they can also be purchased as concentrates and mixed and applied using a pump-up hand sprayer. Granular formulations are not recommended for this use.
Thanks to Joe MacGown for sharing this video and his expertise on ants.
Blake Layton, Extension Entomology Specialist, Mississippi State University Extension Service.
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