32 



of the 7th segment is of large size, and in the hinder part boat- 

 shaped to assist in the discharge of the ootheca ; the 10th segment 

 is notched behind. The ventral plate of the seventh segment is 

 called the lamina srih(/enitalis ; in the male the ventral plate of the 

 9th segment goes by the same name, the dorsal plate of the same 

 segment being called the lamina aupra-analis. 



From beneath the edges of the 10th segment in both sexes spring 

 the cerci, which vary in length and shape, and are usually jointed, the 

 number of segments in Blatta orientaUii and Periplaneta auairalasicB 

 being sixteen. Seeing that these appendages are supplied with 

 large nerves, it would seem that they are not merely ornamental ; 

 perhaps they act as posterior antennae. They often seem to vary in 

 development almost in direct proportion to that of the alar organs, 

 being apparently absent in many wingless forms, though search 

 will reveal them as small plates. 



Besides the cerci the males, in some species, have projecting from 

 the lamina suhi/enitalis, two styles. These are absent from the adult 

 females, though they are present in the nymphs. Perhaps they are 

 homologues of the true legs, and if so constitute one more point 

 tending to demonstrate how old, as a family, the cockroaches are. 



Occasionally a female may be observed with a horny purse- like 

 capsule protruding from the hinder end of her abdomen. This is 

 the ootheca or egg-case. It is formed inside the body of the female, 

 and in Blatta orientalis contains sixteen eggs in two rows of eight. 

 Till that number is complete the case is carried about, and then 

 after a time — some days may-be — it is deposited. In one exotic 

 species the case appears to be wanting, and it is possible that cock- 

 roaches of the past had it not, for Brogniart credits some with an 

 exserted ovipositor. 



When newly hatched the young are white with black eyes ; but 

 they soon assume their proper colour. They closely resemble the 

 adults except for the absence of wings. Post-embryonic develop- 

 ment is slight — another sign of the antiquity of the cockroach 

 group. At from the fifth to the seventh ecdysis (the number is 

 doubtful) the nymph becomes an imago, and in the winged species 

 the organs of flight appear. How long an individual cockroach 

 may live is uncertain, but it is supposed that the term of its 

 existence may under favourable circumstances extend to five years. 



Cockroaches will eat almost anything — even their own dead 

 bodies, or at any rate those of their companions — but as Miall says, 

 "cucumber disagrees with them horribly," and luckily so do phos- 

 phorus-paste and some other insecticides. It must, however, be 

 borne in mind that the cockroach has its place in nature. It is an 

 effective scavenger and so far must be looked upon as a useful 

 insect, and no doubt would be so regarded could we but conquer our 

 rooted dislike to it, and the cockroach get rid of its unpleasant 

 odour. Cockroaches are lovers of warmth and are really numerous 



