312 PHYLUM ARTHROPODA. 



They are omnivorous in their diet, active in their habits, 

 hiding during the day and feeding at night. They are 

 ancient insects, for related forms occurred in Silurian ages ; 

 they are average types, neither very simple nor very highly 

 specialised. Their position is among the Orthoptera, in the 

 same order as locusts and grasshoppers. The young are 

 hatched as miniature adults, except that wings are absent ; 

 in other words, there is no metamorphosis in development. 



FIG. 152. Ventral aspect of male cockroach with the wings extended. 

 An imaginary median line has been inserted. 



A., antennae; E. , eye : P.7\, prothorax ; lyl, first pair of wings; 

 W-"" 2 , second pair of wings ; (_'., cercus ; St., style ; Co., coxa ; 

 7>., trochanter ; F., femur; TV., tibia; Tn., tarsus. 



Skin.- -There is an external chitinous cuticle and a 

 subjacent cellular layer the epidermis or hypodermis 

 from which the cuticle is formed. The newly hatched 

 cockroaches are white, the adults are dark brown. 



Moulting, which involves a casting of the cuticle, of the 

 internal lining of the tracheae, etc., occurs some seven times 

 before the cockroach attains in its fifth year to maturity. 



The muscles which move the appendages, and produce 

 the abdominal movements essential to respiration, are 

 markedly cross striped. 



