XXVI INTRODUCTION. 



the joint forming a right angle with it, they are called divaricale. 

 The claws are often toothed, serrate, or pectinate, and sometimes 

 furnished with membranous appendages which arise near their 

 base. When a claw is either partially or entirely divided so that 

 there is an upper and a lower division, they are then called cleft; 

 rarely, as in many MeloidiB, the upper and lower portions are 

 equal, and both movable. The tip is sometimes divided so that 

 the portions are side by side, in this case the claws are called 

 bifid. When the claws are capable of being drawn back upon 

 the last tarsal joint, they are called chelate ; this form occurs in 

 many Scaraba^idge, and enables the insect to grasp firmly small 

 branches or leaves. Between the claws is seen in many species 

 a small appendage, which is more or less retractile, called an 

 onychium ; this often bears at tip one or more bristle-like append- 

 ages, named 'paronychia. 



ABDOMEN. 



The portion of the body behind the metathorax is called the 

 abdomen, and consists of a series of rings, the normal number 

 of which is nine, though, by coalescence and disappearance, this 

 number is not visible, two being retracted at the base and one 

 at tip; these rings are divided into two portions; the dorsal 

 segments, more or less covered by the elytra, and the ventral 

 segments, visible on the under surface. The union between these 

 takes place on the dorsal surface, and is by membrane, except' in 

 the penultimate pair, which are frequently very closely united. 



The breathing pores, or spiracles, are situated in the connect- 

 ing membranes, or in the upper inflexed portions of the ventral 

 segments. 



The ventral segments are not always opposed to and connected 

 with the corresponding dorsal segments, but are situated differ- 

 ently in the different families, though no use is made of these 

 differences for systematic arrangement. The number of segments 

 visible on the dorsal surface is nearly always greater than on the 

 ventral, and in most cases their structure is less dense and often 

 membranous 



The anal aperture is situated between the last dorsal and 

 ventral segments, and below it, in the same fissure, is situated 

 the genital opening ; each side of this are horny valves, rarely 



