THE INTERNAL ANATOMY OF INSECTS 



109 



(c) Neuroptera. — Myrmeleonid^, Osmylidas, Sisyrid^, and 

 Chrysopidae. In these families the larvae spin silk from the anus. 



(d) Coleoptera. — In the Campodeiform larvas of Stylopidae and 

 Meloidce. 



b. THE FORE-INTESTINE 



The layers of the fore-intestine. — The following layers have been 

 recognized in the fore-intestine; 



The intima. — This is a chitinous layer which lines the cavity of 

 the fore-intestine; it is directly continuous with the cuticula of the 

 body- wall ; and is molted with the cuticula when this is molted. 



The epithelium. — This is a cell layer which is continuous with the 

 hypodermis; it is sometimes quite delicate so that it is difficult to 

 demonstrate it. 



The basement membrane. — Like the hypodermis the epithelium is 

 bounded on one side by a chitinous layer and on the other by a base- 

 ment membrane. 



The longitudinal muscles. — Next to the basement membrane there 



is a layer of longitudinal muscles. 

 The circular muscles. — Out- 

 side of the longitudinal muscles 

 there is a layer of circular 

 muscles. 



The peritoneal membrane. — 

 Surrounding the alimentary 

 canal there is a coat of con- 

 nective tissue, which is termed 

 the peritoneal membrane. This 

 is one of a few places in which 

 connective tissue, so abundant 

 in Vertebrates, is found in in- 

 sects. 



The regions of the fore- 

 intestine. — Several distinct reg- 

 ions of the fore-intestine are 

 recognized; but the extent of 

 these regions differ greatly in 

 different insects. 



The pharynx. — The pharynx 



is not a well-defined region of the 



intestine ; the term pharynx is commonly applied to a region between 



the mouth and the oesophagus; in mandibulate insects the pharynx 



Fig. 125. — Longitudinal section through 

 the head of A nosa plexippus, showing 

 the interior of the left half; mx, left 

 maxilla, the canal of which leads into the 

 pharynx; ph, pharynx; 0, oesophagus; 

 m, m, muscles of the pharynx; sd, 

 salivary duct (After Burges). 



