86 



THE CLASS OF INSECTS. 



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

 crop and proveutriculus, are sometimes absent. 



Of the a2:)]}endages of Hie canal, the first 

 are the salivari/ glands, which are usually 

 long simple tubes, which in the larva, ac- 

 cording to Newport, form the silk vessels. 

 They " empty themselves by a single duct 

 through the spinneret on the floor (labium) 

 of the mouth." In the Ant-lion {Mynneleon) 

 the silk is spun from "a slender telescopic- 

 like spinneret, placed at the extremity of 

 its body," and AVestwood also states that the 

 larva of Chn/sojja spins a cocoon "from the 

 s[)iinieret, at the extremity of the body." 



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 dr3nng 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 

 flowers, before it enters the oesophagus. 

 "Bee-bread" consists of pollen thus moistened and kneaded 

 by the insect. The Honey-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 newl}- 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 verj- large, 

 enveloping most of the other viscera. 



Fig. 45. Alimentary tube of Corydahis cornutus. a, oesophagrus; b, proven- 

 triculus; c, ventriciilus; (/, large intestiue; c, urinary tubes; /, ccecum; </, testis or 

 ovary. — From Lekly. 



