030 



INSECTA. 



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

 (Sp). 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 (fig. 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 

 cliylijic ventricle (M, Chd} } 

 and a terminal portion, 

 which is concerned with 

 the ejection of the faeces 

 (figs. 439, 440). 



The number of regions 

 may, however, be larger. 

 In predaceous Insects, 

 especially in the orders of 

 Coleoptera and Neuroptera, 

 a masticatory stomach or 

 proventriculus (fig. 440, 

 Pv) is inserted between 

 the crop and chylific 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 chylific 

 ventricle also, on 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 

 some Beetles the anterior 

 part has a shaggy appearance from the numerous cseca which 

 project from it (fig. 440 Chd\ and is sharply marked off from 



FIG. 439. Digestive apparatus of A pit melUfica 

 (after L<5on Duf our). Sp, Salivary glands; Oe, oeso- 

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

 tricle ; Re, Malpighian vessels ; R, rectum with 

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



