THE COCKROACH {PeHplaneta americana) 



External Features. 



1. Make a drawing of : 



(i) A dorsal view of the Cockroach with the wings of the right side extended 

 showing : 



(a) The head, bearing the eyes and the antennfe. 

 (&) The prothorax, to the underside of which the first pair of walk- 

 ing legs is attached. The dorsal shield of the prothorax, the 

 pronotum, is large and projects forwards, so that it conceals 

 the short and thin neck ; and the head may also be drawn 

 under it. 

 (c) The mesothorax, to the under side of which the second pair 

 of walking legs is attached. The anterior wings are dark 

 coloured ; they protect the posterior wings, and are known 

 as the wing-covers or elytra or tegmina. They are attached 

 to the dorsal surface. Note that the wing-covers extend 

 beyond the posterior end of the body. The dorsal shield of 

 the mesothorax, the mesonotum, is thin and semi-transparent, 

 being covered by the wing-covers. 

 {d) The metathorax, bearing the third pair of walking legs on its 

 ventral surface and the posterior pair of wings on the dorsal 

 surface. The metanotum or dorsal shield of the metathorax 

 is smaller than, but similar to, the mesonotum. 

 (e) The abdomen. In both sexes there are ten abdominal segments, 

 but in the female some of the segments are modified. A 

 typical abdominal segment has a broad dorsal chitinous plate, 

 the tergum, and an equally broad ventral plate, the sternum. 

 The tergum and sternum meet at an acute angle at the sides 

 of the body, and are united by a soft colourless cuticle. In 

 the abdomen of the female cockroach only eight terga are 

 externally visible. These are the first seven and the 10th. 

 Two more (8th and 9th) are usually concealed beneath the 7th 

 tergum, but they may be seen by extending the abdomen. 

 The 10th tergum is a flat plate notched in the middle of its 

 posterior margin. Beneath it are two triangular chitinous 

 sclerites, the podical plates, between which the anus opens in 

 the middle line. The abdomen of the female is broader and 

 flatter than that of the male. 



In the male the abdomen is narrower and the terga more con- 

 vex than in the female. The first tergum is somewhat small and 

 the sternum is only an oval chitinous plate. Both the terga 

 and sterna of the next six segments are broad chitinous plates ; 



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