A new study published in the journal PLOS ONE shows that the trap jaw ant (Odontomachus brunneus) uses its mandibles to escape from predators. Researchers at the University of Illinois have found that in a significant minority of predator prey interactions, O. brunneus uses its powerful jaws to leap to safety. The pit building ant lion digs traps in the sand and waits for the trap jaw ant to pass its way. This leaping strategy has been hitherto unobserved by any arthropod in its natural environment. The escape mechanism doubles the survival rate for the trap jaw ant and raises new questions on the evolution of escape strategies in the insect world.
The research team collected 228 ant lions and exactly the same number of trap jaw ants. Then two thirds of the ants were left with their crushingly powerful mandibles (from an insects perspective) free from glue, the remaining third were less fortunate. Such is the unwilling sacrifice in the name of science. Science progressed in the arena of a 11 score plus 8 plastic cups.
A total of 228 ordinary cups were filled with sand and an ant lion was added to each. These insects then did what they do best, which is to dig a pit in the sand and wait with the patience of the proverbial African at the bottom of their excavation. The Trap jaw ants were then placed in each cup and the ensuing drama observed. The burning question is which ants would escape and which were going to end up as the next meal for their predator?
Unsurprisingly the ants with functioning mandibles could jump to freedom and those that were incapacitated by glue could not. Interestingly, only 15% of the trap jaw ants that were able to do so jumped their way to escape. For the glued ants survival prospects were indeed grim their survival rate was less than half that of their unglued fellows. Clearly, if your evolutionary prowess has been curtailed by external forces beyond your control, you are going to suffer.
According to the lead author of the research, this shows another example of what biologists term evolutionary co-option. This is a well-documented phenomenon where by an organism learns to use a characteristic designed for one function (the mandibles) is employed to fulfill another function, in this case life preservation