A Camponotus worker stands guard over her leaf nest.

Say “Weaver Ant” to an ant enthusiast and I guarantee you most will imagine the charismatic genus Oecophylla from tropical Africa, Asia, and Australia. Even wikipedia would agree.

But the American tropics also has weaver ants. Several species, in fact.

Wikipedia’s muddled definition aside, weavers are tree-dwelling ants that bind living leaves together with larval silk. These structures remain cool and humid, a perfect refuge from the tropical heat. As weaver ants are defined by behavior, and since the behavior has evolved repeatedly among ants, this is not a taxonomic grouping but a functional one.

During our recent Ecuador excursion we encountered one of the lesser-known weavers. Here’s a nest:

This species is in the genus Camponotus, a group best known for the pesty carpenter ants.

When the nest is disturbed, guards rush out with their gasters facing forward and ready to shoot a stream of formic acid at the intruder. This less-than-endearing habit makes them unpleasant photographic subjects. I had to clean acid off my lenses after taking these shots.

I bring all this up as a suggestion for aspiring myrmecologists. Weaving behavior has evolved enough times to form a replicated natural experiment. Because there are so many separate inventions of weaving (at least 5 or 6), statistical techniques can be used to infer the characteristics that predispose lineages to evolving a weaving lifestyle. If you are looking for a good ant evolution project, say, the sort of work one might do for a Ph.D. dissertation, this topic is ripe for the picking.

photo details:
(top, bottom) Canon 100mm f/2.8 macro lens on a Canon EOS 7D
ISO 200, f/13-14, 1/200 sec exposure, indirect strobe
(middle)Tamron 11-18mm wide-angle zoom on a Canon EOS 7D
ISO 200, f/9, 1/250 sec, hand-held fill flash.