abstracts: entomology 639 



1. "We may distinguish two intergrading types of parasitism among 

 insects. One of these is true parasitism and is represented by the 

 lice, fleas, Mallophaga, many Diptera (Oestridae, Pupipara) and some 

 Hemiptera, which live on mammals and birds and do not destroy their 

 hosts. The other is parasitoidism, which is really a refinement of 

 predatism and is eminently characteristic of large sections of the Hy- 

 menoptera and Diptera (Tachinidae) . It leads sooner or later to the 

 death of the host. The difference between the two types is largely due 

 to differences in the size and vigor of the hosts." 



2. "Parasitoids are of tw^o classes, one of which is best represented 

 by the so-called Parasitica among the Hymenoptera and the Tachinidae 

 among the Diptera, which have no genetic relationship with their hosts. 

 The other class of parasitoids is represented by the Aculeates which 

 have sprung directly from their host species (intraspecific parasitoids), 

 though they may subsequently acquire hosts among other species of the 

 same genus or of other genera and may in turn be the ancestors of para- 

 sitic species." 



3. "The derivation of all the existing Aculeata from primitive in- 

 sectivorous wasp-like ancestors may account for the retention of a 

 rather uniform pattern of behavior among the parasitic species. The 

 parasites, both among the solitary wasps and the solitary bees, behave 

 in a very similar manner, though the former are reared on insect prey, 

 the latter on pollen and honey.* * * " 



4. "The origin of parasitism among the Aculeata may be attributed 

 to urgency of oviposition and temporary or local dearth of the supply 

 of provisions for the offspring." 



5. "In all the different forms of parasitism among the Aculeata, 

 there are traces of the primitive predatism or parasitoidism from which 

 it arose, although in some of the social parasites this is represented only 

 by the aggressive or conciliatory intrusion of the recently fecundated 

 female into the host colony.* * * " 



6. "Although many cases of parasitism are known to occur among the 

 Aculeata, and although many others will doubtless be discovered in the 

 future, nevertheless the total number must be small in comparison with 

 the thousands of nonparasitic species. Contemplation of such a series 

 as we find among the ants, beginning with Formica sanguinea, which 

 is an abundant, vigorous and aggressive species, and ending with Aner- 

 gates airatulus, a small, sporadic, and apparently evanescent species, 

 without workers and with wingless, nymphoid males, suggests that 

 parasitism among the Aculeates tends to such extreme specialization 



