CH. Ill] THE COCKROACH 91 



head of the embryo is uppermost, and the ventral surface 

 of one row faces that of the other, the dorsal surface of 

 each being thus against the side walls of the capsule. 

 When the young are ready to emerge, they push their 

 way out of the capsule at the longitudinal ridge, which 

 is in reality the thickened margins of a slit cemented 

 together. The cement is said to be previously softened 

 by a fluid secreted by the embryos. After the escape 

 of the young the slit is closed up by the elasticity of 

 the walls. The young cockroaches are almost colourless 

 at first, excepting the eyes, which are black. 



The first moulting of the skin takes place immediately 

 after hatching, the second about a month later, the third 

 at the end of the first year ; subsequent moults occur once 

 a year only in the warm weather. The split for the escape 

 from the old integument extends along the middle of the 

 back of the thoracic segments. After each moult the skin 

 is soft and pale, but soon hardens and gets darker in colour. 

 Young cockroaches are always of a lighter tint than adults. 

 Maturity is not reached until the fourth year, according 

 to some observers, though in Bl. germanica the immature 

 stages are passed through more rapidly; nevertheless 

 it is difficult, in the face of the apparent rapid production 

 of new generations of cockroaches, to believe that so long 

 a period is the invariable rule with Bl. orientalis. The 

 young males are at first, like the females, wingless, and 

 only acquire their wings after several moults, but they 

 may at all times be distinguished from the females by 

 the possession of a short pair of styles projecting back- 

 wards from the ninth sternum just below the cerci. 



