198 GLEANINGS FROM NATURE. 



BLATTIDJE. 



From the other families of Orthoptera the Blattidw, 

 commonly known as cockroaches, may be known by 

 their depressed oval form ; their nearly horizontal 

 head, which is bent downward and almost concealed 

 by the broad chest or pro-thorax ; their slender legs of 

 equal length and size; their five-jointed tarsi or feet, 

 and by the absence of either ovipositor or forceps-like 

 appendages at the end of the abdomen. 



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 sep- 

 arate sub-order, the Cursoria or runners. The wing 

 covers or outer wings are leathery, translucent, and, 

 when developed, overlap when at rest; while the 

 wings never exceed the wing covers in length, and in 

 some cases are rudimentary or even wanting. 



From the other Orthoptera the cockroaches differ 

 widely in their habits 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 ob'theca.* These cap- 

 sules vary in the different species, as regards the size, 

 shape, and number of eggs they contain, but they are 

 all similar in structure. Each one is divided length- 

 wise by a membranous partition into two cells. Within 



*See Fig. 44 for illustration of ob'theca of Croton bug. 



