1 66 ELEMENTARY ZOOLOGY 



Examine the softened specimen, and note that at least 

 two additional segments are to be found retracted or tele- 

 scoped into the apparently last segment. The character 

 of these terminal abdominal segments differs in male and 

 female individuals, and specimens of both sexes should be 

 examined. (The males can be distinguished from the 

 females by the peculiar pad-like expansion of the last 

 tarsal segment of the fore legs.) Pull out the retracted 

 segments, and note that they are unevenly chitinized, 

 parts of their surface being simply membranous. Project- 

 ing backwards are several long-pointed processes. The 

 female has but one retracted- segment. Though the 

 females of many insects possess more or less elaborately 

 developed egg-laying organs, this is not the case with the 

 beetles. Look for spiracles near the lateral margins of 

 the dorsal surface of the abdomen. How many pairs are 

 present ? 



Internal Structure (fig.4o). TECHNICAL NOTE. If fresh speci- 

 mens are to be had, kill by dropping into the cyanide bottle (see p. 

 463). Specimens preserved in a 5$ solution of chloral hydrate may 

 be used if necessary. When putting specimens into this solution a 

 small slit should be cut through the body wall to allow the preserv- 

 ative to enter the body cavity. When ready to dissect a specimen 

 cut off the elytra and wings close to the base, and carefully remove 

 all of the dorsal wall of the abdomen and thorax and the median 

 portion of the dorsal wall of the head. Pin ou% ventral side down, 

 under water in a dissecting-dish. 



Note in the median dorsal line of the abdomen a pale 

 transparent longitudinal vessel, the heart or dorsal vessel. 

 Note on each side of it six prominent triangles or " Vs " 

 with apex of each directed laterally, the posteror three 

 smaller than the anterior three of each side. These tri- 

 angles are formed by respiratory tubes or trachea. From 

 each spiracle or breathing-pore there extends into the 

 body a respiratory tube or trachea. These lateral tracheae 

 join a main longitudinal trachea on each side, from which 



