KEY TO CLASSES AND ORDERS OF ANIMALS 39 



12(13) Mandibles long and slender, always as long as the 

 greatest dimension of the head, and frequently nearly 

 twice as long, crescent-shaped or sharply curved toward 

 each other at the tips, or straight slender rods; body 

 widest just behind the posterior pairs of legs. (Corn- 

 stock, 175; Lutz, 53.) Order Neuroptera 



13(12) Mandibles heavy, rarely longer than the greatest 

 dimension of the head; never twice as long. 14 



14(17) Without abdominal prolegs. i5 



15(16) Living in the egg sacs of spiders. (Lutz, 54; Com- 

 stock, 179.) Order Neuroptera (Mantispa) 



16(15) Free living forms. (Comstock, 494; Lutz, 280.) 



Order Coleoptera, in part 



17(14) With abdominal prolegs. 18 



18(19) Prolegs present on the first eight abdominal segments. 

 (Lutz, 56; Comstock, 184.) Order Mecoptera 



19(18) Prolegs absent from at least the first abdominal seg- 

 ment, more frequently from the first two and in this 

 case also from the following one, two, or three segments; 

 always present on the sixth segment. 20 



20(23) Prolegs absent from the first abdominal segment, 

 present on the second and from four to six consecutive 

 segments behind it. 21 



21(22) Body with very numerous long hairs or bristles and 

 numerous shorter tubercles. (Comstock, 218; Lutz, 

 201.) Order Lepidoptera (Megalopygidae) 



22(21) Hairs and tubercles veYy rarely present; when present 

 short and scattered. (Comstock, 610; Lutz, 408.) 



Order Hymenoptera (Terebrantia) 



23(20) Prolegs absent from at least the first two abdominal 

 segments. ^4 



