THE COCKROACH. 345 



by a thin and flexible membrane. Sometimes the great egg- 

 case, which the female carries about for some time before it 

 is laid, is seen protruding between the posterior terga and 

 sterna. The female has movable tegmina^ but they are very 

 small, inasmuch as they do not extend beyond the middle of 

 the metathorax, and are widely separated in the middle line; 

 they are, in fact, mere rudiments of the anterior wings. The 

 posterior wings appear, at first, to be altogether wanting. 

 But the outer extremities of the metanotum, or tergal portion 

 of the metathorax, present triangular areas, in which the in- 

 tegument is very thin, and exhibits markings which simulate 

 the nervures of the wings. There can be no doubt, in fact, 

 that these are undeveloped wings, and they show, in a very 

 instructive manner, that the wings are modifications of that 

 part of the insect skeleton which answers to the pleura, and 

 therefore to the lateral parts of the carapace, of a crustacean. 



The convex dorsal wall of the head of the Cockroach (Fig. 

 97) is termed the epicranium. A median suture — the epicra- 

 nial suture — may be seen, especially in young Cockroaches, 

 traversing it from before backward, and dividing between the 

 eyes into two branches, one of which passes toward the artic- 

 ulation of each antenna. The basal joint of the antenna is 

 attached to a transparent flexible membrane, which occupies 

 an oval space, the antennary fossa, and allows of the free play 

 of the antenna. A little projection of the hard chitinous skel- 

 eton, when it bounds the inferior margin of the fossa, helps 

 to support the joint. On the inner side of, and above the an- 

 tennary fossa, there is an oval fenestra, covered only by a 

 thin and transparent portion of the integument, which allows 

 a subjacent tissue of glistening white appearance to be seen 

 (Fig. 97, I., II., b). These have been regarded as rudimentary 

 ocelli by some entomologists ; but their structure needs care- 

 ful examination before this view can be adopted. 



The transparent cornea of the eye, situated external to 

 and behind the antennary fossa, is elongated, w T ider above 

 than below, and has a concave anterior, and slightly convex 

 posterior, margin. The numerous facets into which the cor- 

 nea is divided are hexagonal in shape, and very small. 



The broad flattened region of the fore-part of the head, on 

 the oral side of the epicranial suture, is the clypeus. It is 

 prolonged in front of the mouth, and with the truncated edge 

 of this prolongation the flap-like labrum is freely articulated. 

 Behind the labrum are two, very stout, curved mandibles, 

 strongly toothed at their extremities (Fig. 97, II., mix). Each 



