INTRODUCTION. 17 



all kinds, as well as on flies and other insects, while the warblers, 

 vireous, and especially the fly-catchers and swallows devour these 

 two-winged insects in great numbers. 



The seven foregoing orders constitute very natural groups, 

 relatively of nearly equal importance, and sufficiently distinct from 

 each other, but connected at different points by various resem- 

 blances. It is impossible to show the mutual relations of these 

 orders, when they are arranged in a continuous series, but these 

 can be better expressed and understood by grouping the orders 

 together in a cluster, so that each order shall come in contact 

 with several others. 



Besides these seven orders, there are several smaller groups, 

 which some naturalists have thought proper to raise to the rank 

 of independent orders. Upon the principal of these, a few 

 remarks will now be made. 



The little order Strepsiptera of Kirby, or Rhipip- 

 TERA of Latreille, consists of certain minute insects, which un- 

 dergo their transformations within the bodies of bees and wasps. 

 One of them, the Xenos Fcchii^ was discovered by Professor 

 Peck in the connnon brown wasp (Polistcs fuscatn) of this coun- 

 try. The larva is maggot-like, and lives between the rings of the 

 back of the wasp ; the pupa resembles that of some flies, and is 

 cased in the dried skin of the larva. In the adult state the 

 Strepsipterous insects have a pair of short, narrow, and twisted 

 members, instead of fore-wings, and two very large hind-wings, 

 folded lengthwise like a fan. The mouth is provided with a pair 

 of slender, sharp-pointed jaws, better adapted for piercing than for 

 biting. It is very difficult to determine the proper place of these 

 insects in a natural arrangement. Latreille put them between the 

 Lepidoptera and Diptera, but thinks them most nearly allied to 

 some of the Hymenoptera. 



The flea tribe {Pidicid^e) was placed among the bugs, or 

 Hemiptera, by Fabricius. It constitutes the order Aptera 

 of Leach, Siphonaptera of Latreille, and Aphaniptera 

 of Kirby. Fleas are destitute of wings, have a mouth fitted 

 for suction, and provided with several lancet-like pieces for 

 making punctures ; they undergo a complete transformation ; 

 their larvse are worm-like and without feet ; and their pupae have 



