252 THE BIOLOGY OF INSECTS 



Another method of obtaining food is practised on Lasius 

 mixtns by a small bristle-tail (Atelura) found in numbers in 

 the ants* nests. Janet (i 896) describes how when one worker- 

 ant is disgorging honey to feed a comrade, the Atelura 

 thrusts itself between the two, *' raises its head, snaps up 

 the droplet, and makes off at once as if to escape merited 

 pursuit." This action might be naturally described as 

 thieving ; the little bristle-tails lurk in the nest where they 

 find shelter and take any opportunity of seizing food. A 

 more specialised method of exploiting ants is practised by 

 the maggots of a Texan fly (Metopina) described by Wheeler 

 as *' messmates " in the nest of a species of Pachycondyla, 

 which feeds its larvae with fragments of insects, these being 

 placed by the workers on the concave ventral surface of the 

 grub within reach of its jaws. Each maggot of Metopina 

 coils itself around the neck-region of the ant-grub, and 

 whenever the latter receives its allowance of insect frag- 

 ments, the fly-larva ''' uncoils its body and partakes of the 

 feast." Both " host " and '' guest " become full fed about 

 the same time, and the latter, enclosed in the former's 

 cocoon, retires for pupation to the tail end of the ant-grub, 

 which completes its transformation before the fxy-maggot, 

 and on emergence from its cocoon leaves an opening 

 through which the fly when subsequently developed can 

 make its way out. 



Many more examples might be given of creatures of 

 other kinds that share the life of the ant communities. The 

 nature of the association varies immensely. On the one 

 hand, we notice the mutually beneficial activities of ants with 

 aphids or with various caterpillars belonging to blue 

 (Lycaenid) butterflies ; these produce from a dorsal gland 

 opening on the sixth abdominal segment, a sweet fluid 

 acceptable to the ants which follow^ the caterpillars about 

 on plants or harbour them in their nests. On the other 

 hand, there are mere thieves like the bristle-tails, mites, 

 and Metopina maggots, or " insect jackals " like certain 

 rove-beetles that devour dead, decrepid and feeble ants, or 

 attack and prey on solitary active ones. Wheeler well 



