138 ENTOMOLOGY 
regular opening and closing movements of some of the spira- 
cles and the rhythmic contraction and expansion of the abdo- 
men. During contraction, the dorsal and ventral walls ap- 
ry 
Tracheal capillary end-network from silk gland of Porthetria dispar. p, peritracheal 
membrane; t, tracheal capillary.x—After WISTINGHAUSEN. 
proach each other (Fig. 176) and during expansion they 
separate. The tergum moves more than the sternum in Cole- 
optera and Heteroptera, and vice versa in Acrididz, Odonata, 
Diptera and aculeate Hymenoptera. The width of the abdo- 
men usually changes but little during respiration, for the ter- 
gal and sternal movements are taken up by the pleural mem- 
Fic. 176. 
Transverse sections of abdominal segments, to illustrate respiratory movements. 4, 
cockroach (Blatta); B, bee (Bombus); s, sternum; t, tergum. The dotted lines 
indicate positions of terga and sterna after expiration; the continuous lines, after 
inspiration.—After PLATEAU. 
branes which, as in the grasshopper, infold at contraction and 
straighten out at expansion. Other respiratory movements 
occur, but they are of minor importance. 
