150 COMPARATIVE ANATOMY 



domestic habits than Periplaneta. The habits of the cock- 

 roach are so familiar as scarcely to require description. It is 

 a nocturnal animal, living by day in crevices and holes, prefer- 

 ably in some warm comer of the house, for it is very susceptible 

 to cold. It is exceedingly voracious, and, as housekeepers 

 know to their cost, attacks every eatable thing that comes in 

 its way. 



The familiar name of "black beetle" is a misnomer, for the 

 cockroach belongs to the order Orthoptera^ and has not the 

 hard glossy wing-cases which, among other characters, are dis- 

 tinctive of the true beetles or coleoptera. The name " cock- 

 roach " seems equally inappropriate, but it is probably a corrup- 

 tion of the Spanish cucardcha^ of which kakerlak is the Dutch, 

 and cancrelat the French equivalent. 



Students of insect anatomy will find a full and admirably 

 lucid account of the anatomy and physiology of the cockroach 

 in Miall and Denny's volume on this animal.* Nothing more 

 will be attempted in this place than to contrast its structure as 

 a typical insect with that of the Crustacea described in the two 

 last chapters. 



The animal is evidently an arthropod ; it has a segmented 

 body protected by a firm chitinous exoskeleton. Certain of 

 the segments are provided with jointed appendages, which bear 

 a sufficiently close resemblance to the walking limbs of a cray- 

 fish ; the mouth is furnished with three pairs of jaws which are 

 evidently modified limbs, and internally the blood-vascular 

 system, the reduced ccelom, the nervous system, and other 

 characters, correspond in a general way with the anatomical 

 arrangements of the crustacean. But the insect has many 

 characters peculiar to itself. The three regions of the body, 

 head, thorax, and abdomen, are very distinct, the head in par- 

 ticular being separated from the thorax by the intervention of 

 a slender neck. The thorax comprises only three segments, 

 and these alone bear walking-limbs, the abdomen being legless 

 except for the anal cerci, which are proved by development to 

 be the representatives of the eleventh pair of abdominal limbs. 

 Moreover, the two posterior segments of the thorax bear each 

 a pair of membranous expansions of the integument or wings, 



* The "Structure and Life-History of the Cockroach," by L. C. Miall 

 and Alfred Denny. London : Lovell, Reeve & Co. ; Leeds : Richard 

 Jackson, 1886. 



