530 



INSECTA. 



cavity, open one or more pairs of tubular or racemose salivary glands 

 (8p). In many of the suctorial insects, the end of the oesophagus is 

 dilated into a sack with thin membranous walls and a short stalk, the 

 suctorial stomach ; in others into a more uniform dilatation, known 

 as the crop (tig. 439, Oe). The intestine which follows the oesophagus 

 is sometimes straight and sometimes coiled ; it varies exceedingly 

 in accordance with the mode of life. It is always at least divisible 



into a longer portion, 

 which is concerned in di 

 gestion, the mesenteron or 

 chi/Ufic ventricle (M, CJid), 

 and a terminal portion, 

 which is concerned with 

 the ejection of the freces 

 (figs. 439, 440). 



The number of regions 

 may, however, be larger. 

 In predaeeous Insects, 

 especially in the orders of 

 Coleoptera and Neuroptera, 

 a masticatory stomach or 

 proventriculus (fig. 440, 

 Pr) is inserted between 

 the crop and chylinc ven- 

 tricle ; this is of globular 

 form, and has powerful 

 muscular walls. It is lined 

 by a specially thick chitin- 

 ous cuticle, which is beset 

 with strong bands, teeth, 

 and bristles. The chylinc 

 ventricle also, 011 which 

 especially the digestive 

 glandular layer is developed 

 at the expense of the mus- 

 cular layer, is sometimes 

 divided into several re- 

 gions, as for example in 



FIG. 439. Digestive apparatus of A/iis uieHiflca 

 (after Leon Duf our). S/>, Salivary glands; OP, ffiso- 

 phagus with crop-like dilatation ; M, chylinc ven- 

 tricle ; Re, Malpighiau vessels ; If, rectum with 

 so-called rectal glands ; G. Dr, poison glands. 



some Beetles the anterior 

 part has a shaggy appearance from the numerous ca?ca which 

 project from it (fig. 440 CM}, and is sharply marked oft' from 



