Page:Insects - Their Ways and Means of Living.djvu/230



débris. The insects thernselves will give an answer to the question if several of thern are placed in glass tubes and covered with earth; but, to understand the cicada's technique, we must first study the rnechanisrn of its digging tools, the front legs. The front leg of a rnature cicada nyrnph (Fig. J x6 A) is

Fro. 6. The digging organ, or front leg, of the mature cicada nymph A, right le[g, inner surface (4 times natural size). B, the tarsus (Tar) bent inward at right angles to the tibia (Tb), the posi- tion in which it is used as a rake Cx, basal joint or coxa; Tf, trochanter; F, retour; Tb, tibia; Tar, tarsus, with two terminal daws

cornposed of the sarne parts as any other of its legs. The (hird segment from the base, which is the.femur (F), is large and swollen, and has a pair of strong spines and a cornb of srnaller ones projecting from its lower edge. The next segment is the tibia (Tb). It is curved and terrninates in a strong recurved point (B). Finally, at- tached to the inner sur- face of the tibia, well up from its terminal point, is the slender tarsus (Tar). The tarsus can be extended beyond the

tibial point when the insect is walking or clirnbing, but can also be turned inward at a right angle to the latter, as shown at B, or bent back against the inner surface of the tibia. Let us now return to the insects in the earth-filled tubes, where they are industriously at work. It will be seen that they are using the curved, sharp-pointed tibiae as picks with which to loosen the earth, the tarsi being turned back and out of the way. The two legs, working alternately, soon accurnulate a srnall rnass of loosened rnaterial in front of the insect's body. Now there is a

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