EXTERNAL PARTS OF A COCKROACH ii 



and also the terga with the sterna. The orifice of each spiracle 

 IS directed backwards. • A large spiracle will be found between 



Fig- 9.— Cockroach (in last larval stage) escaping from old skin. X 2J. 



the fore and mid legs, and a smaller one between the mid 

 and hind legs. It will be desirable to examine the spiracles 

 with a lens, though they can be 

 seen by the naked eye. 



Male and female cockroaches 

 differ most conspicuously in the 

 degree of development of the wing- 

 covers and wings, which are very 

 imperfect in the female. The 

 abdomen is broader in the female 

 than in the male, and the feelers 

 shorter. The hinder abdominal 

 segments differ in the two sexes. 

 The seventh sternum is divided in 

 the female, but not in the male. 

 The abdomen apparently ends with 

 the seventh sternum in the female, 

 but with the ninth sternum in the 

 male. The ninth sternum bears a 

 pair of styles in the male, which are 

 wanting in the female. The male 

 is slighter and weaker, feeds less 

 greedily, and stands higher than 

 the female, whose abdomen trails 

 on the ground. Immature cockroaches have neither wing- 

 covers nor wings in either sex. There is no resting-stage 



Fig. 10. — Cast skin of older 

 larva (" pupa ") of cock- 

 roach. X 2^. 



