RELATIONS WITH OTHER ARTHROPODA. 67 
insect attacked. Thus it is able to destroy house flies, butterflies, 
mosquitoes, etc., only when the latter are hurt or disabled, as 
under ordinary conditions they are much too swift for the ants to 
catch. In the same manner nearly all forms of beetles are strong 
enough to escape from the ants when caught, and their external 
covering is so hard that the ants can make no impression upon it; 
but an injured beetle of any kind is very quickly overcome by the 
numbers of the ants, and his body is finally cleaned out of the shell 
piecemeal. Newly emerged adult beetles of many species are often 
captured by the ants before their chitinous integument has hardened, 
and they are then an easy prey. 
Cutworms and hairless caterpillars found upon the surface of the 
ground are destroyed in great numbers; but the ants will not burrow 
into the ground after hidden cutworms, and most hairy caterpillars 
appear to be invulnerable to them. Web-spinning caterpillars are 
also safe from their attacks, and the spiny, mealy projections sur- 
rounding coccinellid or ladybeetle larvae appear to protect these 
latter very effectively. Insects and other small related animals which 
the ants can meet upon even terms are, however, almost always over- 
come; not so much on account of the individual valor of the Argen- 
tine ants as by reason of their overpowering numbers. 
Nests of the social wasps, Polistes sp., which were brought into our 
laboratory as food supplies for cultures of Pediculoides, were quickly 
found by foraging workers, and the latter soon killed and removed 
all of the wasp larvae and pupae that could be reached. Many of the 
cells in the comb of Polistes were entirely or partially open so that 
the ants had ready access to the insects inside. As the prey in this 
case was too large to be handled by individual ants, as many as two 
or three dozen would unite in removing a single wasp pupa or larva. 
Even the adult wasps, just emerging from the cells, were set upon by 
the ants before they had attained sufficient strength to escape by 
flight. More and more of the ants would get on these adult wasps 
until the latter were helpless and were dragged away, still alive, by 
scores of the worker ants. So anxious were the ants to get at these 
wasps that when the latter were placed on top of a fruit jar standing 
in a tray of water the ants swam the 3 inches of fresh water, climbed 
the glass sides of the jar, and continued their attacks as before; nor 
could they be made to desist until oil of sassafras was placed upon 
the water. 
The nests of mud-dauber wasps, Pelopoeus sp., were also brought 
into the laboratory for the same use as the Polistes. The mud- 
dauber larvae were of course inaccessible to the ants, but parasitic 
flies 1 which emerged from these were seized by the ants as fast as 
1 Identified by Mr. C. H. Tyler Townsend as a species of PachyopMhalmus, 
