WHEELER— THE PARASITIC ACULEATA. 21 



the parasitic relationships four types can be recognized. One of 

 these, corresponding to Wasmann's category of " compound colo- 

 nies " is represented by a number of small species which live in 

 little nests that communicate with the nests of the host by tenuous 

 galleries. The two species bring up their brood separately, but the 

 workers consort with one another freely and amicably in the gal- 

 leries and chambers of the host. The relations of parasite and host, 

 where they have been determined, are much like those exhibited 

 between certain ants and their myrmecophiles (symphiles). The 

 most typical of these guest ants is our North American Leptothorax 

 cmcrsoni, the behavior of which I have elsewhere described in de- 

 tail. From the accompanying table (Table III.), in which all the 

 known guest ants and their hosts are listed, it will be seen that none 

 of the former is congeneric with its host. Emery's statement ( 1909 ) , 

 however, that : " The myrmecophilous ants are not derived from 

 forms allied to their host species, but from other genera or even 

 from other subfamilies," is not strictly true, though in all proba- 

 bility the guest-ants have developed, as he contends, from preda- 

 tory thief-ants, of which quite a number of species are known to 

 nest in the walls of the nests of termites and larger ants and to prey 

 on their brood. 



The three other types of parasitism, representing Wasmann's 

 category of " mixed colonies," are the slave-makers, temporary and 

 permanent social parasites, which agree in living so intimately with 

 their host in the same nest that the two species bring up their broods 

 in common. The differences between the three types is, however, 

 very striking when we follow the development of the parasitic 

 colony, although it is founded in every case by a single recently 

 fecundated female, or queen, that succeeds in entering and estab- 

 lishing herself in the nest of the host species. The queen slave- 

 maker, at least in species like Formica sangiiinea, breaks into the 

 host nest and appropriates and fiercely defends a portion of the host 

 brood till it matures and surrounds her with a number of loyal 

 workers, which are then able to rear the brood hatching from her 

 eggs. The workers produced by such a queen have the extraordi- 

 nary habit of making periodical, organized raids during the summer 

 months on other colonies of the host species (usually Formica 



