52 THE LARVA OF THE BLOW-FLY. 



and the mesenteron and metenteron (uiihi), developed from the 

 hypoblast. 



The terms which have been applied to its several sections 

 are such as indicate incorrect homologies with the alimentary 

 canal in vertebrates. The stomodceum consists of the pharynx, 

 oesophagus, crop, and of a portion of the proventriculus. 



The Crop. — This is the sucking stomach of Weismann ; it is 

 more properly termed a food-sac. In manducatory insects 

 the term is applied to a uniform enlargement of the oesophagus, 

 which in phytophagous Orthoptera and Coleoptera frequently 

 occupies nearly the whole thorax and a considerable portion of 

 the abdomen. In suctorial insects the crop is a diverticulum 

 of the ventral surface of the oesophagus, usually with a long 

 tubular neck. The neck of the crop often appears as the 

 direct continuation of the gullet, whilst the second part of the 

 oesophagus ascends almost at right angles to the first, and 

 enters the proventriculus. 



In the imago in the Diptera, Hymenoptera, and Lepidoptera 

 the crop is the well-known honey-bag ; it is situated in the 

 abdomen, and when distended with food occupies a considerable 

 portion of that cavity. 



The Proventriculus of suctorial, corresponds with the gizzard 

 of manducatory insects ; it is usually a thick- walled, almost 



Description of Plate I. 



Fig. I. — The Alimentary Canal of the Adult Larva, 3-inch objective : fv, proventri- 

 culus ; c g, cxcal glands; f/i, chyle stomach; /, proximal, and P, distal intes- 

 tine ; f///>, Malpighian vessel ; r, rectum ; /r, tracheae. 



Fig. 2. — Section of a Portion of the Crop, ^-inch objective : c:t, cuticle ; ep, epithelial 

 cells ; //, peritoneal coat ; £, ganglion cells. 



Fig. 3. — Proventriculus : mn, median, or stomogastric nerve ; ^, proventricular 

 ganglion ; c^, gastric caeca ; c/i, chyle stomach. 



Fig. 4. — A Longitudinal Section through the Proventriculus : a; oesophagus ; tr, 

 trachea ; i d, imaginal disc ; pv, proventriculus ; ch, chyle stomach. 



Fig. 5- — Transverse Section through one of the Gastric Cceca, ^-inch objective. 



Fig. 6. — Transverse Section through the Chyle Stomach ; c n, cell nests ; gc, parietal 

 cells. 



Fig. 7. — A Transverse Section through the Distal Intestine, ^-inch objective : c, amoe- 

 boid cells. 



Fig. 8. — Transverse Section of a Malpighian Tube, |-inch objective. 



Fig. 9. — Transverse Section of a Salivary Gland of Resting Larva, showing the 

 formation of the Membrana Propria. 



