354 ORDERS OF PTILOTA. 



The species which are truly indigenous in England are of com- 

 paratively small size, and are generally found in woods ; but the 

 species which frequent our houses, occasionally in such myriads 

 as to cover the floors of the lower apartments in the metropolis 

 at night, are of more southern origin, the ordinary species 

 (B. orientalis) being a native of Asia. It is probable that its 



Blatta orientalis (male and female). 



introduction was owing to the navigation of the Levant, being 

 brought over in ships' cargoes. It is to the same cause that the 

 American cockroach {B. americana), a much larger species than 

 the ordinary one, is gradually acquiring a settlement in London 

 and other ports. But the ravages of these insects in warm climates 

 appear to be far greater than amongst us, as appears from the 

 account given by Drury of the B. gigantea, which is an inhabitant 

 of the West Indies. 



But the most singular circumstance connected with these in- 

 sects consists in the manner in which the eggs are deposited. 

 Instead of these ])eing laid singly, as is generally the case amongst 

 insects, nature has given the females a most curious instinct for 

 the preservation of their offspring. In fact, the females deposit a 

 large oblong mass, convex at the sides, and flattened at the edges, 

 which serves as a case for an entire family of young blattai. This 

 mass, which is of large size, being nearly half the entii'e size of 

 the abdomen of the female, is borne about by her for a considerable 

 period. At first it is white, but gradually becomes dark brown. 

 Although composed of a single piece, the edge along one side is 



