234 



MANUAL OF ZOOLOGY. 



The integument of the Insecta, in the mature condition, is 

 more or less hardened by the deposition of chitine, and usually 



forms a resisting exoskel- 

 eton, to which the mus- 

 cles are attached. The 

 segments of the head are 

 amalgamated into a single 

 piece, which bears a pair 

 of jointed feelers or an- 

 tennae, a pair of eyes, 

 usually compound, and 

 the appendages of the 

 mouth. The segments 

 of the thorax are also 

 amalgamated into a single 

 piece ; but this, neverthe- 

 less, admits of separation 

 into its constituent three 

 somites (fig. 80). These 

 are termed respectively, 

 from before backwards, 

 the "prothorax," "meso- 

 thorax," and " metatho- 

 rax," and each bears a pair 



Fig. 80. Diagram of Insect a Head, carrying of jointed legS. In the 

 the eyes and antenna; Prothorax, carrying great majority of InSCCtS, 

 the first pair of legs ; c Mesothorax, carrying & . J . J , r , i 



the second pair of legs and first pair of wings ; d the QOrsal archCS OI the 

 Metathorax, with the third pair of legs and the mac/-\fhrkrc] Y nnrl rnpfa 

 second pair of wings; * Abdomen, without .limbs, niCSOtnoraX and meta- 

 but having terminal appendages subservient to thorax glVC Origin each 

 reproduction. to a pair of wingS. 



Each leg consists of from six to nine joints. The first of 

 these, which is attached to the sternal surface of the thorax, is 

 called the " coxa," and is succeeded by a short joint, termed 

 the "trochanter." The trochanter is followed by a joint, often 

 of large size, called the " femur," and this has articulated to it 

 the " tarsus," which may be composed of from two to five joints. 



The wings of Insects are membranous " flattened vesicles, 

 sustained by slender but firm hollow tubes, called ' nervures/ 

 along which branches of the tracheae and channels of the cir- 

 culation are continued." (Owen.) In the Cokoptera (Beetles) 

 the anterior pair of wings become hardened by the deposition 

 of chitine, so as to form two protective cases for the hinder 

 membranous wings. In this condition the anterior wings are 

 known as the "elytra," or "wing-cases." In some of the 

 Hemiptera this change only affects the inner portions of the 



