EXTERNAL PARTS OF A COCKROACH 9 



pair of well-developed wings in the male. When not in use, 

 they are folded up fanwise, beneath the wing-covers. The 

 female has no wings, but a reticulated pattern on the outer 

 margin of the metathoracic tergum represents a pair of wings 

 which have disappeared. The wing-covers of the male, though 

 stiff in the cockroach, represent a pair of true wings, which 

 are membranous and useful for flight in many insects. The 

 thoracic sterna are much encroached upon by the bases of the 

 legs, and cannot well be seen without a lens. Three pairs of 

 legs are carried on the thorax, one pair to each segment. 

 They regularly increase in size from the first to the third, but 

 hardly differ otherwise. Each is divided into the five parts 

 usual in insects. The coxa (haunch) or basal joint is broad 

 and flattened. The troclianter is a small piece connecting the 

 coxa with the femur (thigh), the elongate third joint of the leg. 



Fig. 6.— Profile of male and female cockroach. 



The tibia (shin) succeeds the femur, and is of about the same 

 length. Then comes a five-jointed tarsus (foot), which ends 

 in a pair of claws. 



The abdominal segments consist of dorsal plates (terga) and 

 ventral plates (sterna). The first abdominal segment has only 

 a vestige of a sternum. The hindmost plates are somewhat 

 irregular, and the arrangement is different in the two sexes. 

 A pair of jointed cerci project from the end of the abdomen 

 in both sexes, and in the male a pair of slender styles can be 

 seen between the cerci. In the abdomen of the female eight 

 terga (1-7, and 10) are externally visible. Two more (8, 9) are 



