20 WHEELER— THE PARASITIC ACULEATA. 



parasite seizes the prey or food for itself, or, regarding the situation 

 merely from the standpoint of the individual life-history of the 

 parasite, we may say that it is predacious either in its first larval 

 stage or as an adult on the egg or young larva of the host. The 

 host egg or larva constitutes an obstacle to the parasite's enjoyment 

 of the prey or bee-bread, and as the parasite is a true ir>sect bol- 

 shevik and member of the I. W. W. its life purpose is completely 

 expressed in the impudent imperative : " Get out, I want your 

 place." Nor is it surprising that long before the Russian Soviets 

 the parasitic wasps and bees had learned that the quickest way to 

 remove a living obstacle is to kill it. 



There is some difificulty in deciding which of the two types of 

 parasitism represented in the diagrams is the more primitive. Prob- 

 ably the more aggressive Nysson type was the earlier as indicated 

 by the behavior of Psammochares rufipcs and pcctinipcs. On this 

 supposition the role of assassin, directed not only against the host 

 larva, but also against any competing larva of its own species, was 

 acquired later by the larval parasite as a result of neglect on the 

 part of the mother to destroy the egg of the host. The same type 

 of behavior, however, is also seen in many other insects when more 

 than one egg is laid by the mother in a very limited supply of food, 

 e. g., among the larval egg-parasites (Proctotrupids) and the cater- 

 pillars that live in the heads of composite flowers (Rabaud, 1912, 

 1914). In the larval egg-parasites the large, sickle-shaped jaws 

 are beautifully adapted for the purpose of killing competing indi- 

 viduals of the same species, and the similar mandibles described by 

 Graenicher in larval bees of the genera Stelis, C(rlioxys and Tric- 

 pcoliis are equally useful in destroying both the competitors of the 

 same species and the host larva. 



The social parasites are most abundantly represented and have 

 been most extensively studied among the ants. The literature on 

 the subject is so voluminous that I am unable to deal with it here. 

 Much of it is cited in my ant book (1910), where the subject is con- 

 sidered in greater detail, and in the first volume of W'asmann's 

 " Gesellschaftsleben der Ameisen " (1915). As would be expected, 

 the conditions become very complex when a social organism such 

 as a colony of ants becomes parasitic on another colony. Among 



