INTEODUCTION. 3 



which have been variously conjectured to be organs of hearing, 

 touch, and smell. Their structure differs so much in different 

 insects that it is highly probable that they may serve one purpose 

 in one insect and another in another. They are composed of 

 a very variable number of joints from two or three to thirty or 

 forty, and they may be so short as scarcely to project in front of 

 the head, or they may be several times as long as the whole body. 

 They differ very much in shape and structure also, and are called 

 filiform, serrated, pectinated, clavate, ramose, lamellated, bifurcate, 

 etc., accordingly. Not unfrequently some of the terminal joints 

 are much thickened, sometimes into a very distinct knob. Some- 

 times the joints are very distinctly separated, and at other times 

 the antennae are covered with down or bristles, so that the separa- 

 tion between the joints is hardly visible. The basal joint is called 

 the scape, and it is often much longer than the other joints, 

 occasionally measuring half the length of the antennae, or even 

 more. 



In addition to the antennae, insects are provided with one or 

 two pairs of small jointed organs called labial and maxillary palpi. 

 These form part of the mouth organs, and are probably organs 

 of taste, and perhaps also of touch. Many insects are provided 

 with large mandibles, while others, which live entirely on liquid 

 food, are furnished with a long proboscis instead. In some insects 

 both mandibles and a proboscis are developed. 



The head is regarded by Professor Huxley as morphologically 

 consisting of six segments (or somites), of which, however, the 

 existence of only four can be demonstrated. The three following 

 segments form the thorax, which is sharply separated in the perfect 

 insect from both the head and the abdomen. The three segments 

 of the thorax are called prothorax, metathorax, and mesothorax 

 above, and prosternum, mesosternum, and metasternum beneath. 

 The upper portion of the thorax is frequently called the pronotum. 



The three pairs of legs are attached to the three segments of 

 the thorax respectively. The legs are composed of five parts : the 

 coxae, or hips, the trochanters (a small joint between the coxae 

 and the femora), the femora, or thighs, the tibiae, or shanks, 

 and the tarsi, or feet. The tarsi are composed of five joints, but 

 are liable to numerous modifications, and one or two joints are 

 frequently undeveloped. The last joint of the tarsi usually ter- 

 minates in a double claw. In leaping insects, the coxae and 

 femora are sometimes very largely developed. The legs may be 



