STRUCTURES OF COCKROACHES. 61 



for living in the narrow crevices and cracks which they inhabit. 

 This peculiar structure was doubtless acquired when living be- 

 neath stones and bark before man came into being, and has 

 enabled them, like the earwigs, to hide in the crevices of ships 

 and especially in cargoes of fruit, and tropical and semitropical 

 forms have thus been scattered to all parts of the earth. 



The legs of a cockroach are of a peculiar structure in that they 

 have the coxae very large and flattened, thus serving to protect 

 the ventral surface of the thorax ; femora long, compressed, their 

 lower border with two keels or margins which are usually armed 

 with spines, these varying much in size and number; tibia? heav- 

 ily armed with spines both above and beneath ; tarsi 5-jointed, the 

 first joint much the longest, the last one with two claws, with or 

 without a lobe or arolium between them, the others usually each 

 with a pad or pulvillus beneath. The structure of the legs enables 

 the cockroaches to run with such great swiftness that they seldom 

 use the wings in trying to escape pursuit, and has given the name 

 Cursoria or runners to the suborder of which they form the only 

 family. 



From the other Orthoptera the Blattida? differ widely in the 

 manner of oviposition, as the eggs are not laid one at a time, but 

 all at once in a peculiar capsule or egg case called an ootheca. 

 These capsules vary in the different species as regards the size, 

 shape, and the number of eggs they contain, but they are all very 

 similar in structure (Fig. 31). Each one is divided lengthwise 

 by a membranous partition into two cells. Within each of these 

 cells is a single row of cylindrical pouches, somewhat similar in 

 appearance to those of a cartridge belt, and within each pouch is 

 an egg. 



The female cockroach often runs about for several days with 

 an ootheca protruding from the abdomen, but finally drops it in 



a suitable place and from it the 

 young, in time, emerge. While this 

 method of oviposition is the one 

 practiced by all the species of com- 

 mon occurrence in the United 

 Fi -. 31- ootheca of Pcrifiaucta States, there seem to be exceptions 



atnci-icana (L.) a, side; b, end view. 



Natural size indicated by outline fig- fo it, aS Dr. C. "V. RlleV has 1'6- 



ure. (After Howard.) 



corded (ISOla) the fact of an in- 

 troduced tropical species, Panchlora CAibensis (Sauss.), being 

 viviparous, the young emerging alive from the body of the parent, 



