A Hair Trigger

Trigger hairs (arrows) on the mandibles of a Trap Jaw Ant Image from

Trigger hairs (arrows) on the mandibles of a Trap Jaw Ant (Daceton armigerum)
Image from GRONENBERG*

Trap Jaw Ants use their antennae to locate prey and enemies. Touching a non-nestmate insect with their antenna can initiate an attack. In an attack, the jaws snap shut at over 80 mph and must be aligned to the victim to be effective. If the victim is hit by only one mandible before the other, a blow will bounce the victim away rather than puncture the victim.

To align properly with the victim, the trap jaw ant, Odontomachus, maintains antenna contact while it adjusts its body position. Once aligned, the ant retracts its antennae while stepping forward. When trigger hairs on the mandibles contact the victim, a reflex causes the jaws to snap shut. The time elapsed from antennal retraction to jaw snap is about 12 milliseconds (a hundredth of a second).**

Clipping the two terminal segments from one of the pair of antennae will result in a misalignment between the trap jaw ant and its victim.** This results in the victim being harmlessly bounced away rather than being trapped between the two mandibles.

If the trigger hairs on the mandibles are clipped, the ant will move closer to the victim before snapping its jaws, or the snap of the jaws may not be triggered at all. Trap Jaw Ants have a true “Hair Trigger”.

*WULFILA GRONENBERG. 1996. THE TRAP-JAW MECHANISM IN THE DACETINE ANTS DACETON ARMIGERUM AND STRUMIGENYS SP. The Journal of Experimental Biology 199, 2021–2033.

**Ehmer, B. & Gronenberg, W., 1997. Proprioceptors and fast antennal reflexes in the ant Odontomachus, Formicidae, Ponerinae. Cell Tissue Res. 290, 153–165.

About jjneal

Jonathan Neal is an Associate Professor of Entomology at Purdue University and author of the textbook, Living With Insects (2010). This blog is a forum to communicate about the intersection of insects with people and policy. This is a personal blog. The opinions and materials posted here are those of the author and are in no way connected with those of my employer.
This entry was posted in behavior, by jjneal, Taxonomy. Bookmark the permalink.

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