154 



The rings of the abdomen overlap each other and are capable of great 

 extension and depression so that these insects seem to be pre-eminently 

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

 The legs are of peculiar structure in that they are long and more or less 

 flattened, thus enabling the cockroaches to run with surprising swiftness, 

 so that the family has been placed by some writers in a separate sub-order, 

 the Cursoria, or runners. The wing covers, or tegmina, are leathery, trans- 

 lucent, and, when well developed, overlap when at rest ; while the wings 

 never exceed the tegmina in length, and in some cases are rudimentary or 

 even wanting. 



From the other Orthoptera the Blattkhe differ widely in the manner of 

 oviposition, as the eggs are not laid one at a time, but all at once in a pe- 

 culiar 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 similar in structure. Each one is divided 

 lengthwise by a membraneous partition into two cells. Within each of 

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

 pearance 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 common occurrence in the United 

 States, there seem to be exceptions to it, as Dr. C. V. Riley has recently 

 recorded the fact* of an introduced tropical species, Panchlora viridis, 

 Burm., being viviparous, the young emerging alive from the body of the 

 parent, and a careful dissection of the latter showing no trace of either 

 eggs or ootheca. 



All young cockroaches resemble the parents in form but are wholly wing- 

 less, the wings not appearing until after the fifth or last moult. The young 

 are often mistaken for mature individuals by persons who have not made 

 a careful study of the life history of the insects ; and those of one or two 

 well known and common forms, have, in the past, even been described or 

 figured as distinct, wingless species by some of the leading entomologists 

 of the country. 



To the paleontologist, interested in tracing back the ancestry of insects, 

 the Blattidse become at once a group of surpassing interest, for the oldest 

 known insect, Pahroblatiina douviUei, Brong., is a cockroach recently de- 

 * Insect Life, III., August, 1891, 443. 



