COCKROACHES 131 



NUMBERS AND DISTRIBUTION OF COCKROACHES 



The cockroaches belong to the family Blattidse, which is 

 rather closely related to the family of grasshoppers, or 

 locusts. The family Blattidse contains nearly a thousand 

 known species and it is thought that eventually several 

 thousand more species, now unknown, will be added to the 

 list. Fortunately, most of these species occur in the woods 

 and fields away from human habitations. In the United 

 States only four or five species have become domestic. 

 A few species are found in the fields and woods. In 

 tropical countries, however, the domestic species are 

 numerous, and the so-called wild species are abundant and 

 many of them are striking in color and of large size, one 

 species having a wing expanse of more than six inches. 

 As we have already pointed out, at least one species oc- 

 curs in the far North. 



Of the four species in the United States that are con- 

 sidered pests, one of them, the "black-beetle" of Europe 

 is commonly said to have come, originally, from Asia. 

 One other, the so-called croton-bug, or German cock- 

 roach, is supposed to be of European origin. As a matter 

 of fact, the origin of these two forms is very obscure and 

 nothing absolutely definite is known about their native 

 home. The third species, the Australian cockroach, is 

 undoubtedly a native of Australia and came to this coun- 

 try in ships. The fourth one, the American cockroach, is a 

 home species native to the tropical and sub-tropical parts 

 of America. Thus it happens that three-fourths of the 

 species of roaches common in our households have been 

 introduced from foreign countries and have already 

 become as injurious as in their original homes. 



