120 BRANCH ARTHROPODA 



muscular system varies widely in the different forms. In the 

 caterpillars there is a " sirhple worm-like arrangement of 

 segmentally disposed longitudinal and ring muscles," while in 

 the more active forms, as flies and bees, the muscular system is 

 complicated. The muscles are composed of fine, cross-striated 

 fibers, forming masses of various sizes, and are attached to the 

 rough inner surface of the exoskelton. The muscles are trans- 

 parent and have great contractile power. 



Digestive System. — The alimentary tube (Fig. 93), which may 

 be coiled much or little, varies greatly. It is about the length 



Fig. 93. — Internal anatomy of Calopte'nus fe'mur-ru'brum: at, Antenna 

 and nerve leading to it from the " brain " or supra-osophageal ganglion 

 (sp); oc, ocelli, anterior and vertical ones, with ocellar nerves Icadhig to 

 them from the " brain "; ae, esophagus; m, mouth; lb, labium or under lip; 

 if, infra-esophageal ganglion, sending three pairs of nerves to the man- 

 dibles, maxillee, and labium respectively (not clearly shown in the engrav- 

 ing); sm, sympathetic or vagus nerve, starting from a ganglion resting 

 above the esophagus, and connecting with another ganglion (.sgr) near the 

 hinder end of the crop; sal, salivary glands (the termination of the salivary 

 duct not clearly shown by the engraver); nv, nervous cord and ganglia; 

 ov, ovary; ur, urinary tubes (cut off, leaving the stumps); ovt, oviduct; 

 sb, sebaceous gland; be, bursa copulatrix; ovt', site of opening of the oviduct 

 (the left oviduct cut away); 1-10, abdominal segments. All other organs 

 labeled in full. (Drawn from his original dissections by Mr. Edward 

 Burgess.) (From Packard's "Zoology," Henry Holt & Co., Publishers.) 



of the body in carnivorous forms, and longer in the herbivorous 

 insects. It consists of a mouth, esophagus, crop, gizzard (the 

 chitinous lining of which is toothed for grinding the food), a 

 digestive stomach, and an intestine. There may be one or two 

 pairs of salivary glands, and usually two or more pairs of 

 gastric caeca containing glands supposed to supply digestive 

 fluids. The intestine usually consists of a small intestine and a 

 large intestine, the two regions of the latter being the colon and 

 the rectum. The Malphighian tubules, fine tubes connected 

 with the intestine at the beginning of the rectum, take the place 



