CLASSIFICATION 



15. Diptera. Metamorphosis indirect. Month parts typ- 

 ically suctorial, but modified for piercing, lapping, rasping, etc. 

 Prothorax small. One pair of wings (mesothoracic), mem- 

 branous, transparent, with few veins; wings rudimentary or 

 absent, however, in most of the parasitic species ; hind wings 

 represented by a pair of knobbed threads, or balancers. Lar- 

 vae cruciform, with the head frequently reduced to a mere 

 vestige with or without a pair of mandibles, and usually with- 



FIG. 27. 



Papilio troilus. A, larva; B, larva suspended for pupation; C, chrysalis. 

 Natural size. 



out true legs, though pseudopods may be present. Example, 

 Tipula (Fig. 29). About forty thousand described species. 



1 6. Siphonaptera (Aphaniptera). Metamorphosis indi- 

 rect. Head small. Eyes simple or absent. Mouth parts 

 suctorial. Body laterally compressed. Thoracic segments 

 subequal. Wings absent or at most quite rudimentary. Lar- 

 vae with a head, mandibulate, apodous. Parasitic insects. 

 Example, Ctenocephalus (Fig. 30). One hundred and fifty 

 species. 



17. Hymenoptera. Metamorphosis indirect. Mouth parts 

 at the same time mandibulate and suctorial. Prothorax usu- 

 ally small. Wings four, similar, membranous, transparent, 



