Pheidole obscurithorax and Pheidole parva: Let the Big Girls Play

Pheidole obscurithorax is the largest Pheidole species in Florida, whereas Pheidole parva is one of the smaller exotic species that is new to the area. Whereas the majors of P. obscurithorax can have total lengths of more than 6 mm and head widths of more than 1.7 mm, the tinier P. parva majors have head widths of only 0.8 mm and total lengths at around 2 mm.

This discrepancy in scale came into play when a P. obscurithorax colony barged into the bait meant for a nearby P. parva colony. The intrusion of the P. obscurithorax workers prompted the build-up in the P. parva soldiers, who by the end of the melee made up almost all the visible workers. This in turn summoned the very large P. obscurithorax soldiers, and I thought they would easily push aside the smaller ants.

But I was surprised at the efficiency of the P. parva soldiers, who swarmed the much larger ants and seemed to concentrate their attacks on the legs of the latter. Within a few minutes there were 4 or 5 P. obscurithorax soldiers pinned and being dismembered in the area.

This was not accomplished without cost though, and the bodies of dead and mutilated P. parva soldiers was everywhere in evidence.