376 SANITARY ENTOMOLOGY 



Bldberus, Leucophaea, etc., occur in houses, the main forms with which 

 the sanitarian has to deal comprise but four species, Blatta orientalis, 

 Blattella germanica, Periplcmeta americana, and Periplaneta awstralasiae, 

 especially the first two. These four domesticated species are easily sep- 

 arated, being very distinctive in appearance, the two species of Periplaneta 

 only offering any difficulty in this respect. But even their differentiation is 

 easy by the figures and descriptive notes given herein, and by use of the 

 following key, which is based upon easily appreciated characters. 



KEY TO THE FOUE PRINCIPAL HOUSEHOLD COCKEOACHES 



1. Size small, total length usually no more than one-half inch; pronotal' 



disk with two, longitudinal, parallel, blackish stripes ; last ventral 

 segment of the abdomen of both sexes entire (fig. 72). 



Blattella germanica (Linnaeus) Caudell. 



Size medium or large, rarely much less than one inch in length, usually 



more ; pronotal disk not marked as above ; last ventral segment of 



the abdomen of the male entire, of the female longitudinally 



divided — 2. 



2. Size medium, length about one inch ; color black or dark brown, the 



pronotum unicolorous above ; tegmina and wings abbreviated, in 

 the male covering about two-thirds of the abdomen, in the female 

 the tegmina forming mere lateral pads and the wings absent (fig. 

 71). Blatta orientalis (Linnaeus). 



Size large, generally considerably more than an inch in length; color 

 reddish brown, the pronotum above distinctly bordered with yel- 

 lowish color ; tegmina and wings fully developed in both sexes — 3. 



3. Tegmina with a yellowish, humeral stripe in distinct contrast to the 



color of the rest of the surface ; central dark area of the pronotal 



disk sharply outlined — Periplaneta australasiae (Fabricius). 



Tegmina not marked as above ; central area of pronotal disk less 



sharply outlined (fig. 73) Periplaneta americana (Linnaeus). 



Blatta orientalis (Linnaeus) (fig. 71) 



One of the most prevalent and widely distributed roaches is the Blatta 

 orientalis of Linnaeus, in the Old World sometimes called the black beetle, 

 a name now fortunately less used, for though it is black, the roach is 

 not a beetle. The common name oriental roach is preferable for this 

 species. 



Blatta orientalis is a medium sized roach of a blackish color. The 

 male is an inch, or a little less, in length, of a very dark-brown color, and 

 furnished with both tegmina and wings, covering about two-thirds of the 



