14 SOME Sol ill INDIAN INSECTS, ETC. [CHAP. I. 



called the propulsory apparatus or commonly (but incorrectly) the 

 heart, may often be seen, especially in internal-feeding larvae. 

 beneath the skin in the central part ol the back. By the pulsatory 

 action of this tube, the circulatorj fluid is drawn into the small 

 openings (osteoli) occurring along that portion (ventriculus) which 

 lies within the abdomen and driven forward through the thoracic 

 and cephalic portions (aorta Figure 2, Ao) into the head, whence 

 it flows back outside the tube and into the various organs of the 

 body, rhe fluid itself is often improperly called blood but more 

 correctly chyle; it is usual lj colourless, or slightly tinted green 01 

 yellow and consists of two parts, a fluid part (serum or haamol) mph) 

 in which swim active amoeboid bodies (amcebocites ; also called 

 leucocytes, phagocytes, etc.). 



. Uimentary System* 



The Alimentary System lies along the middle portion of an 

 insect throughout the whole length oi the latter. The food is 

 received through the mouth into the oesophagus or pharynx (Figure 

 2, F) whence it passes into the crop and theme (through the pro- 

 ventriculus when this is present) into the stomach or midgut (Figure 

 2, Mes), and from thence into the small intestine (In) and on into 

 the large intestine or rectum (Rt). At the junction of the stomach 

 and small intestine are found the Malpighian tubules (Mp), which 

 are almost always present, though variable in number and hence 

 sometimes used for classificatory purposes; they are believed to 

 function, much like kidneys in the higher vertebrates, for the 

 excretion of urates from the system. 



Fat Glands timl Slink Glands. 

 Of the internal organs connected with the Alimentary System 

 it is only necessary to mention here the Fat Bodies, which are 

 often immensely developed, and the Stink Glands which sometimes 

 open into the rectal aperture, as in many Coleoptera. 



Reprodtu 1 1 VC System. 

 In its main features, the type of the reproductive s\siem is 

 COmparativelj simple. In tin- male the internal organs imimsi ,,| 

 testes ami accessory glands (both usually paired hut sometimes 

 multiple, though always symmetrical) and paired seminal vesicles 

 leading into a common ejaculatory duct which in turn leads into 



* In this and similar accounts the reader must rememl general 



descriptions an possible in a 1 1, if this natur and thai more advanced treatises tnusl 



be consulted lor the elncidation of details. The Alimentary System in particular is 

 variable in structure and the rehtiw' proportions "flirts in different insects. 



