Wasps, Bees, and Ants 



477 



classification, together with their (mostly) small size and the slight and 

 hardly recognizable differences on which their scientific distinction rests, 

 would make their systematic study nearly impossible for the amateur. On 

 the other hand the interesting character and the biologic and economic 

 importance of their habits of life make it desirable to know as much as may 

 be about their life-history. I shall, therefore, give the little space which our 

 book can afford to these insects almost exclusively to a consideration of the 

 ecologic aspects of their study. 



FIG. 670. Hairy caterpillar killed by parasitic ichneumon-flies which have left the 

 body through small holes in the skin. (Natural size.) 



The superfamilies and families meant to be included among the insects 

 referred to when the general term "parasitic Hymenoptera" is used are 

 (using Ashmead's classification) the 

 superfamily Proctotrypoidea, a great 

 group of mostly minute species, many 

 of which pass all their immature life 

 within the eggs of other insects; the 

 superfamily Chalcidoidea, an even 

 larger group, also of small species, 

 but with a few forms which are gall- 

 makers and not parasites; and the 

 superfamily Ichneumonoidea, including 

 the larger parasitic Hymenoptera. 

 Each of these superfamilies includes a 

 number of families, and the three 

 together comprise an enormous host 

 of mostly little-known insect species. 

 At the present time much diversity 

 exists in the arrangement of the various 

 parasitic families in entomological 

 manuals. In the ol^er books the para- 

 sitic habit has been looked to as in- 

 dicating an affinity of relationship 

 among them all ; in more recent books 

 and papers is adopted an arrangement 

 proposed by Ashmead which indicates a nearer relationship on the part of 



FIG. 671. Caterpillar killed by Hymen- 

 opterous parasites which have issued 

 from the cocoons attached to the skin 

 of the caterpillar; upper figure one of 

 the adult parasites. (After Jordan and 

 Kellogg; caterpillar and cocoons natu- 

 ral size; adult parasite much enlarged.) 



