HOW TO KNOW THE IMMATURE INSECTS 



10b. Prothorax shorter than and smaller than mesothorax or meta- 

 thorax; cerci wanting; tarsi 2 or 3-segmented; labial palp 1 -seg- 

 mented; resemble aphids in shape. Fig. 60. Order CORRODENTIA 



The psocids, booklice, or dustlice are the mem- 

 bers of this order which includes about 1,000 de- 

 scribed species. They feed upon the paste of book 

 bindings, fragments of animal and decaying veg- 

 etable matter, and cereal products. They are found 

 in houses, on tree trunks, under bark, in bird's 

 nests, etc. Eggs are laid in small groups on bark 

 or leaves and are protected by a meshwork of 

 silken threads. After hatching, the changes of de- 

 velopment are slight. Six instars are recorded in 

 certain species. 



Fig. 60. Peripsocus 

 phocopterus. 



11a. Long axis of head and mouth parts usually vertical; in one fam- 

 ily (Blattidae) the mouth parts project caudal and in another 

 family (Phasmidae) ceptalo-ventrad; among the Phasmidae the 

 prothorax is much smaller than the mesathorax or metathorox 

 and the legs are greatly elongated; the mouth parts of all the 

 species are of a generalized chewing type; antennae with many 

 segments. Fig. 61 Order ORTHOPTERA page 69 



The number of recorded species is 

 about 22,000. They possess greatly de- 

 veloped powers of running and leap- 

 ing. The eggs are mostly cylindrical 

 and some are deposited in oothecae. 

 In many Mantidae and Locustidae the 

 nymphs shed a membranous covering 

 shortly after hatching. The wing pads 

 are usually present in the second or 

 third instar. There are commonly 6 in- 

 stars passed in the nymphal stage. 



Fig. 61. a, German cock- 

 roach, Blattella germanica 

 (L.); b, Melanoiflus differ- 

 entialis (Thomas). 



35 



