OUTLINES OF ENTOMOLOGY. 



459 



are comparatively small, being modified into simple sheaths, often of 

 metallic hardness and luster, beneath which the longer and broader 

 membranous lower wings are compactly folded, except during flight. 

 In the majority of other insects the wings are translucent or transpar- 

 ent, more closely veined and not clothed with scales or hairs. The 

 other organs of locomotion are the legs. In fully developed insects 

 these are invariably six in number. Some of our most conspicuous but- 

 terflies, it is true, seem to have but four, but the absence of the front 

 pair is only apparent, and close examination will reveal them folded 

 close against the breast and perfectly formed, though small and use- 

 less. The legs of insects are modified in many ways to adapt them for 

 running, leaping, burrowing and swimming, according to the habit of 

 the species. Each leg consists of six parts : a large flattened joint 

 called the coxa, which is attached to the body ; this is succeeded by a 

 joint which is very variable in form, usually small, but in some species 

 large and having the appearance of an ornamental appendage, and is 

 termed the trocanter (plural trochantines) ; next to this is a long and 

 often very stout thigh or femur (plural femora) succeeded by the shank 

 or tibia (plural tibicc), to which is attached the foot or tarsus (plural 

 tarsi), consisting of from two to five small joints, and in many species 

 terminating in a pair of sharp claws, sometimes with a pad-like suck- 

 ing disk, termed a pulvillus, between them. 



The abdomen in insects is composed 

 of ten remaining segments. In most 

 species, however, the hindermost 

 rings are modified into the apparatus 

 for reproduction and are drawn more 

 or less within the body, so that only 

 from five to seven joints can be clearly 

 distinguished. It is in this part of 

 the body that the form of the typi- 

 cal ring can be traced with greater 

 Legs.oTiginai and adapted; a, leg of preda- accuracy than in any other region, as 



ceous beetle ; a, coxa; b, trochanter; c, femur; 



d, tibia; e, tarsus; /, tarsal claws; g. tibial the Segments are HOt apparently COll- 

 spur; B, leg of bee, clothed witbbair for col- Qolidated ag in the tll0iax but ar e 

 lecting pollen; C, front leg of mole cricket, lu- 

 ted for burrowing in the earth; a, femur: b, tibia; held together quite lOOSely with elaS- 

 c, tarsus; D, leg of water beetle adapted to . 



tic membrane. 



fig 6. 



swimming. 



Along each side of the body is a row of more or less conspicuous 

 orifices. These are the openings through which the insect breathes, 

 and are termed stomata or stigmata or spiracles. They conduct to air- 

 tubes, to which more particular reference will be made in a succeeding 



