146 OUR HOUSEHOLD INSECTS 



better opportunities of establishing itself. It is a 

 common species on board ships. An Australian species 

 also appears to be beginning to spread. Again, Blatta 

 germanica, a closely allied form, called in America the 

 "Croton Bug," is known all over the United States, 

 and sometimes gets a footing in Britain. In a baker's 

 shop at Leeds it established itself, and is said to have 

 been introduced by soldiers after the Crimean war, 

 coming with them to the barracks, and being thence 

 conveyed to the bakery in bread baskets. According to 

 Hummel, this species assists its young to escape from 

 the egg-case. He introduced a female into a bottle con- 

 taining one of the cases ; she immediately seized it and 

 slit it open with her jaws, and tore off the enveloping 

 membranes of the contained young. 



Besides house cockroaches, we have in this country 

 field cockroaches, i.e., indigenous species that habitually 

 live out in the open and do not attach themselves to 

 mankind. They are smaller than P. orientals, and may 

 be found in sandy places and amongst dead leaves and 

 other vegetable rubbish. They have sufficient superficial 

 resemblance to P. orientalis to be recognisable as coming 

 into the same category, although their colour is generally 

 much paler. In addition to these, large numbers of 

 species occur wild in other countries ; but why just those 

 particular species mentioned above, and especially P. 

 orientalis itself, should have become dependent upon the 

 human race, while so many others have either not 

 attempted to do so, or have not succeeded if they have 

 attempted, is still shrouded in mystery. The chief 

 peculiarity by which orientalis is distinguished from its 

 fellows, viz., the apterous condition of the female, seems 

 rather as though it might militate against its chances 

 than favour them. 



