. Elementary entomology. Insects. 22 ELEMENTARY ENTOMOLOGY Legs. The legs articulate with the sternum and pleurum and con- sist of five parts, - - the coxa, trocJiantcr, femur, tibia, and tarsus. The base of the coxa forms the joint of the leg to the body, which is either of the ball- and-socket or of the hinge type. The tro- chanter is a small, in- termediate segment, which in parasitic Hy- menoptera is double. Tdr Tb. Tr Emp ~Cla FIG. 24. Typical insect leg Cx, coxa ; Cla, claws ; Emp, empodia ; F, femur ; Tar, tarsal segments ; Tb, tibia; Tr, trochanter. (After Snodgrass, United States Depa
. Elementary entomology. Insects. 22 ELEMENTARY ENTOMOLOGY Legs. The legs articulate with the sternum and pleurum and con- sist of five parts, - - the coxa, trocJiantcr, femur, tibia, and tarsus. The base of the coxa forms the joint of the leg to the body, which is either of the ball- and-socket or of the hinge type. The tro- chanter is a small, in- termediate segment, which in parasitic Hy- menoptera is double. Tdr Tb. Tr Emp ~Cla FIG. 24. Typical insect leg Cx, coxa ; Cla, claws ; Emp, empodia ; F, femur ; Tar, tarsal segments ; Tb, tibia; Tr, trochanter. (After Snodgrass, United States Department of Agriculture) The * femur is the largest segment in the leg, and in grass- hoppers and other jumping insects is strongly developed by the muscles with- in. The tibia is usu- ally long and slender. The tarsus is usually composed of several similar segments, five being the typical number. The last segment usually bears a pair of sharp claws in adult insects and a single claw in larvae. Between the claws of most adult insects is a little pad, called a pulvillus, or empodium, a suckerlike organ which enables them to walk upon smooth surfaces and to cling to objects when upside down. Nearly all adult and most larval insects have three pairs of thoracic legs, but many boring and parasitic larvae have lost them entirely. The legs are often greatly modified according to the habits of the insect, not only for locomotion, but for grasping, digging, and other purposes. The legs of most beetles are typical of walking insects. In jumping insects, like the grasshopper and flea beetles, the hind femora are greatly developed. In digging insects, such as the mole cricket and cicada nymphs, the tibia and tarsus of the fore- legs are developed as shovels. The forelegs of many predacious insects, such as the mantis, assassin bugs, and others, bear teeth upon the opposing surfaces of the tibia and femur, which make them efficient grasping organs. The legs of the bees are highly developed :
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