Fig. 9.—Nerve-end­ing in skin of Stratio­mys larva. h, hairs; b, their chi­tin­ous base; c, nuc­leus of gen­er­at­ing cell; g, gan­glion cell. × 250. Copied from Viallanes.

Fig. 10.—Diagram of sen­sory hair of Insect. Cc, chi­ti­nous cu­ti­cle; h, hair; c, its gen­er­at­ing cell; g, gan­glion cell; bm, base­ment-mem­brane.

The chitinous cuticle is often folded in so as to form a deep pit, which, looked at from the inside of the body, resembles a lever, or a hook. Such inward-directed processes serve chiefly for the attachment of muscles, and are termed apodemes (apodemata). A simple example is afforded by the two glove-tips which lie in the middle line of the under-surface of the thorax (p. 58, and fig. [27]). In other cases the pit is closed from the first, and the apodeme is formed in the midst of a group of chitinogenous cells distant from the superficial layer, though continuous therewith. Many tendons of insertion are formed in this way. The two forked processes in the floor of the thorax (p. 58, and fig. [27]) are unusually large and complex structures of the same kind. In the tentorium of the head (p. 39, and fig. [17]) a pair of apodemes are supposed to unite and form an extensive platform which supports the brain and gullet.

Fig. 11.—Nymph (in last larval stage) escaping from old skin. × 2 1/2.