KEY TO CLASSES AND ORDERS OF ANIMALS 41 



34(35) With fleshy protuberances on the ventral side of the 

 abdominal segments and a single spine at the posterior 

 end. First thoracic segments apparently longer than 

 the second and third together. (Comstock, 614; 

 Lutz, 411.) Order Hymenoptera (horntails) 



35(34) Without fleshy protuberances on the abdomen. 36 



36(37) Forms of considerable size in later stages, boring in 

 various plant structures or in decaying wood. (Lutz, 

 280; Comstock, 494.) Order Coleoptera, in part 



37(36) Forms of very small size even in later stages. 38 



38(39) Segmental setae short. Feeding in stems of grains. 

 (Lutz, 414; Comstock, 629.) 



Order Hymenoptera, in part (joint worms) 



39(38) Segmental setae long, body very slender. Living in 

 refuse; very minute. (Lutz, 279; Comstock, 490.) 



Order Siphonaptera 



40(33) Head inconspicuous, frequently retractile inside the 

 thoracic segments; body tapering at the anterior end, 

 without rudiments of thoracic legs. 41 



41(42) Larvae free living. (Comstock, 413; Lutz, 229.) 



Order Diptera, in part 



42(41) Parasitic or living in cells or in nest prepared by the 

 adults. 43 



43(44, 45) Parasitic on other arthropods or on plants. Gall 

 formers. (Lutz, 406; Comstock, 601.) Order Hymen- 

 optera, in part or (Lut^, 229; Comstock, 444.) 



Order Diptera, in part 



44(43, 45) Parasitic on mammals beneath the skin, in the nose 

 or stomach. (Lutz, 229.) Order Diptera, in part 



