M 



THE CLASS OF INSECTS. 



tine, and the colon and rectum. The latter part, as well a/ the 

 crop and proventriculus, is sometimes absent. / 



Of the apj^endages of the canal, tje first 

 are the salivary glands, which are /usually' 

 l(Mig simple tubes, which in the jArva, ac- 

 cording to Newport, form the sA' vessels. 

 They " empty themselves by a Angle duct 

 through the spinneret on tlie fl<or (labium) 

 of the mouth." In the Ant-\ion..{JI>jnneleon) 

 the silk is spun from "a slender telescopic- 

 like spinneret, placed at tlw extremity o/ 

 its bod}'," and Westwood alsJ states that the 

 larva of Chrysopa spins a cocoon "from the 

 spinneret, at the extremity of the bod}'." 



These silk glands when taken out of the 

 larva, just as it is about ready to transform, 

 are readily prepared as "gut" for fish-lines, 

 etc., by dr3'ing on a board. 



In the Bees these glands are largely de- 

 veloped to produce a sufficient amount of 

 salivary fluid to moisten the dry pollen of 

 Fig. 45. flowers, before it enters the oesophagus. 



"Bee-bread" consists of pollen thus moistened an,d kneaded 

 by the insect. The Ilonej^-bee also dissolves, by the aid of the 

 salivary fluid, the wax used in making its cells. Newport 

 believes this fluid is alkaline, and forms a solvent for the other- 

 wise brittle wax, as he has seen this insect " reduce the per- 

 fectly transparent thin white scales of newty secreted wax to 

 a pasty or soapy consistence, by kneading it between its man- 

 dibles, and mixing it with a fluid from its mouth, before apply- 

 ing it to assist in the formation of part of a new cell." 



Insects have no true liver ; its functions being performed 

 "by the walls of the stomach, the internal tunic of which is 

 composed of closely-aggregated hepatic cells." (Siebold.) In 

 the Spiders and Scorpions, however, there is a liver distinct 

 from the digestive canal. In the Spiders it is very large, 

 enveloping most of the other viscera. 



Fig. 45. Alimentary tube of Corydalus cornutus. «, oesophagus; 6, proyen- 

 triculus; c, ventriculus ; rf, large intestiue ; e, urinary tubes ;/, coecum ; (/, testis or 

 ovary. — From Leidy. > 



