16 

 COCKROACHES 



The first cockroaches were brought to England, perhaps from 

 the East, in the sixteenth centur}^ ; at first they spread slowly, 

 but later became ubiquitous ; they were of the species Blatta 

 orientalis, now known as the common cockroach. In the nineteenth 

 century two other species, Blattella germanica, the ' German ' 

 cockroach (not a native of the country 

 from which it takes its name), and Peri- 

 planeta americana, the American cock- 

 roach, perhaps from tropical America, 

 were introduced. The first two are found in 

 houses ; the third generally only in the 

 larger buildings, such as warehouses and 

 hotels ; P. australasice also occurs, chiefly 

 in glasshouses. The use of DDT as an 

 insecticide has now removed cockroaches 

 from many buildings, and they are difficult 

 to obtain. All cockroaches are nocturnal, 

 and if a light is suddenly switched on 

 they run back to shelter ; occasionally 

 one will freeze instead, and is easily 

 caught. They prefer warm places, and are 

 omnivorous, eating not only human food, 

 but paper, hair, and leather. They find 

 their food by smell. 



w.g..^ 



aJb.^ 



~ah. 7 



, — can. 



'0&. 10 



Fig. i6i. — A female of 

 the common cockroach. 

 The body is somewhat 

 compressed so as to 

 show the membranes 

 between the abdominal 

 terga. The legs have 

 been removed. 



The simplest way of telling the adults a6.i-a*.io, Abdominal terga, a/., 

 . , , ' • -i •x^ • antenna ; can., anal cerci ; 



of the three common species is by tneir h., head; th.i, prothoradc 



^ ,, . . 7->7 // • • t, 1 tergum ; th.2, mesothoracic 



wmgs and their size. Biatta is an men long, tergum; th.^, metathoracic 



T^, 77 i-,,i ,^ ^ ^£ • i_ J tergum; w.g., vestige of fore 



Blatella a little more than half an inch, and wing. 



Periplaneta an inch and a half. The wings 



of Blatella and Periplaneta (which are not Hkely to be confused) 



cover the abdomen ; those of the male Blatta leave three or 



four segments exposed, and those of the female are vestigial. 



In the general structure they are ahke. 



2Z- 



