lo ENTOMOLOGICAL NEWS. [January, 



by the slender oesophagus with the crop, situated in the thorax, 

 or more posteriorly. Following the crop is the prove7itnculus, or 

 gizzard, a grinding organ with strong muscular walls. The 

 stomach, veJitriculus , or chylijic ventricle succeeds, situated in the 

 abdomen. After this is the intesti^ie, which may sometimes be 

 subdivided into three parts, the ileum, or small intestine (imme- 

 diately following the stomach), the coloti, or large (thicker) in- 

 testine, and the rectum, or terminal part. The crop and gizzard 

 are sometimes absent. 



The alimentary canal is composed of three coats, the outer, 

 or peri to7ieal, the middle, or muscular, and the inner, or mucojis. 

 The canal is held in place by retractor muscles, but principally 

 by exceeding numerous branches of the main tracheae (Packard). 



The appendages of the alimentary canal are the salivary, the 

 ccecal, and the anal glands, and the inalpighian vessels. The 

 salivary glands open near the mouth. In some larvae (caterpil- 

 lars) they are the source of the silk. The caecal glands open 

 into the stomach ; their secretion resembles the pancreatic secre- 

 tion of backboned animals. The anal glands open into the hind 

 part of the intestine; their secretion is usually offensive and con- 

 stitutes an organ of defense. The malpighian vessels are long, 

 slender tubes opening into the fore part of the ileum; they are 

 analogous to the kidneys of higher vessels. Insects have no 

 true liver, its functions being performed by the walls of the 

 stomach (Siebold quoted by Packard). 



The circulatory system consists of a dorsal vessel or heart, an 

 aorta, and a few branches of the latter. The heart is a jointed 

 organ of a varying number of chambers, one behind the other, 

 corresponding in position to the segments (of the fore part of the 

 abdomen) in which they are situated. The chambers are sepa- 

 rated by valves permitting motion in but one direction — from 

 behind forwards. A pair of lateral valves in each chamber allows 

 entrance, but prevents exit. The heart is contained in a cavity — 

 Xho. pericardial sin7is, separated from the other organs by a mem- 

 brane—the pericardial diaphragm, pierced by many openings. 

 At its fore end the heart opens into the aorta, a simple tube run- 

 ning to the head where it may or may not divide into short 

 branches. In either case the vessels apparently end in the head 

 as open tubes. The circulation is believed to be as follows: 

 By the successive contraction of the chambers of the heart, the 



