CLASSIFICATION 



21 



for boring, sawing or cutting. Larvae with complex mouth 

 parts and frequently abdominal legs. Phytophagous. Ex- 

 ample, Tremex (Fig. 31). 



FIG. 30. 



FIG. 31. 



Cat and dog flea, Ctenocephalus canis. A, larva (after KUNCKEL D'HERCULAIS) ; 

 B, adult. Length of adult, 2 mm. 



Suborder Aculeata (Heterophaga, Petiolata). Abdomen 

 petiolate or subpetiolate ; first abdominal segment transferred 

 to the thorax. Ovipositor 

 often modified to form a 

 sting. Larvae apodous. Ex- 

 ample, Apis (Fig. 277). 



Interrelations of the 

 Orders. The modern clas- 

 sification aims to express 

 relationships, and these are 

 most clearly to be ascer- 

 tained by a comparative 

 study of the facts of anat- 

 omy and development. 



The most generalized, or 

 primitive, insects are the 

 Thysanura. e Subtracting 



their special, or adaptive, peculiarities, their remaining charac- 

 ters may properly be regarded as inheritances from some 

 vanished ancestral type of arthropod. This primordial type, 



Tremex columba. A, imago; B, larva 

 (with parasitic larva of Thalessa attached). 

 Natural size. After RILEY. 



