THE ANATOMY OF THE LARVA 47 



The internal organs are of typically insect plan, and 

 will be most easily understood by considering each system 

 separately. 



Digestive System. — Apart from the gnathites or foot-jaws, 

 which, although of the ordinary masticatory type are rather 

 complex organs, the intestinal canal is of the simplest form, 

 consisting of a narrow oesophagus, which leads into a wide, 

 perfectly straight tube, commonly spoken of as the stomach, 

 which extends to the end of the sixth abdominal segment. 

 Into its thoracic end open the ducts of the hepatic glands, 

 which, when examined m section, are seen to be broad 

 crypts communicating with the • stomach by so wide an 

 opening as to almost appear as diverticula ; and into its 

 distal, where the tube contracts before the commencement 

 of the rectum, open the five Malphigian tubules, which are 

 slender tubular glands, differing in no way from those of the 

 adult. Lying close to the oesophagus in the head are the 

 two salivary glands, but they are not easy to demonstrate, 

 except in section, and the same remark applies to the rectal 

 glands, which lie beside the rectum in the last segment. 

 The mouth parts consist of an upper lip or lahriim, in the 

 form of a convex crenated plate, armed with numerous 

 hairs, and a longer and narrower lower lip, or labium, of 

 somewhat similar structure. Between these are placed the 

 two pairs of foot-jaws, the mandibles above and the maxillae 

 below. Each mandible consists of a somewhat pyriform 

 plate, the wider end of which forms an articulation with the 

 lateral structures of the mouth ; while the narrower end is 

 formed into a rather complex set of dentations divided into 

 two groups, the anterior of which are small and claw-like, 

 and mainly adapted for holding the prey, while the hinder 

 set are better adapted for cutting and crushing. The 

 appendage is further provided with brushes of peculiarly 

 formed hairs, and has, about the middle of the anterior 

 border, two large jointed processes or hairs, which probably 

 are tactile or gustatory in function. The maxilla is a plate 

 of somewhat quadrangular outline, the anterior border 

 being curved and its corners rounded off. It is richly pro- 

 vided with hairs, some of which have a curiously compound 



