I’ve been spending a lot of time looking at the ant-acacias that I study for my PhD. The other day I cam across the most intriguing insect living among the ants on one of the acacias. There are several different ant species involved in a mutualism with the plant. The acacia provides housing and food (through sugary nectar secreted from special glands), and the ants provide patrolling protection against hungry mouths and mandibles that might chance to nibble on the plants.
One particular ant is very aggressive and an extremely good partner for the plant. This is a cocktail ant (Crematogaster mimosae) who provides regular patrolling and rushes to defend the plant when it is disturbed.
However, no arrangement is perfect and every relationship is subject to infiltration in nature. Many different creatures exploit the ant-plant mutualism for their own selfish ends. I found one of these remarkable creatures the other morning. While watching the ants tending scale insects on the young shoots of an acacia I noticed a bright green form moving among them. At first I thought I was seeing things – perhaps the result of spending too much time in the sun?
A closer look revealed that they little green person was indeed an alien intruder in the form of a beetle. This beetle lives among the ants as a total freeloader. It cons them through a mixture of tactile and no doubt chemical communication into thinking that it is one of them. It even taps them on the head in the right way and the hapless ants regurgitate food for it!