Mexican Elongate Twig Ant

Elongate Twig Ant (Pseudomyrmex gracilis) patrolling a 

Caesar weed (Urena labata) blossom. Photo by Bob Peterson

At MOSI Outside, we don't love all bugs. We especially aren't fond of the ones that bite or sting you for no particular reason, like the non-native Mexican Elongate Twig Ant (Pseudomyrmex gracilis). The species was first reported in Dade County, Florida in the 1960's and before that, it had only been found in Texas, the Caribbean, Mexico and south to South America. They have now been found in several states in the Southeast.

These ants live inside twigs, in burrows that were left from other species. Their long and slender bodies are perfect for navigating narrow spaces inside very small twigs where they tend to eggs and immature ants. While wandering around, they tend to fall or wander onto people with some regularity.

The genus of Pseudomyrmex ants are formicine ants (Formicinae). These ants have a toxin that is a cocktail of formic acid combined with protiens, and peptides. Each species has a slightly different mixture, some of which are more or less painful to humans. The toxin is applied by way of an acidopore, which is essentially a nozzle for spraying venom that can be found at the end of the abdomen. The spray of formic acid in small amounts created by ants can go unnoticed by humans unless the ants have first bitten their victim and then spray the venom into the bite. That is when things become un-fun.

Pseudomyrmex gracilis on dayflower.
Photo by Bob Peterson

The bite and venom combination of the Elongate Twig Ant can be exceptionally painful, reminiscent of a wasp sting. Additionally, the pain for the venom seems to last longer than bites or stings of other garden insects. In the case of MOSI Outside, both keepers develop large, painful welts when bitten and these bites can remain painful for several hours or even as long as a full day. At times, it feels precisely like the ant is still biting you even though you have already removed it. To make ths species even less loved, when bound up in clothing (like the inside of a shirt) these ants will keep biting and applying venom until the victim manages to get the ant out of their clothing.


Learn more here:

• Worldwide Spread of the Graceful Twig Ant, Pseudomyrmex Gracilis (Hymenoptera: Formicidae): James K. Wetterer
• Featured Creatures- Pseudomyrmex gracilis: IFAS
• Pseudomyrmex gracilis: Ant Wiki