258 INSECTS AND MAN 



practically assured, and factors of climate alone will, for 

 the present, keep it within reasonable bounds. Whether 

 it will eventually become hardened and capable of with- 

 standing the rigours of a northern climate and so over- 

 running the globe, is a conjecture that time alone can 

 answer. 



COCKROACHES 



One of the commonest insects of British households is the 

 " black beetle " (fig. 69). How the insect earned its nick- 

 name would be hard to say. It is not even related to the 

 beetles, being a member of the order Orthoptera and of the 

 family Blattidce, though here, again, some early scientist 

 must have been at fault, for the Latin word " blatta," from 

 which the family name is derived, means a beetle. Peri- 

 planeta orientalis, for that is the insect's name, is a native 

 of tropical Asia, and no better illustration could be taken 

 of the manner in which an insect, and a tropical one at 

 that, can adapt itself to conditions so totally at variance 

 with those of its original habitat. Once confined to some- 

 what arbitrary limits in the Orient, this insect has followed 

 man throughout the world till, at the present time, it is 

 practically cosmopolitan. Climatic conditions have not set 

 a limit on its travels as they have, up to the present, upon 

 another household pest, the Argentine ant ; perhaps some 

 day it too may travel in the wake of commerce to temperate 

 latitudes, then it may quite conceivably rank as the worst 

 household pest of all. Common, for several centuries, in 

 all seaport towns of this country, it was only at a later 

 date that the common cockroach spread inland, and, at the 

 present day, it may be found in practically every village 

 in England. 



As a household pest it, for the most part, frequents 

 kitchens, bake-houses, and all places where the warmth is 

 greatest, and, being nocturnal in its habits, it is not so often 

 encountered as might be supposed. But it is not necessary 



