EXTERNAL ANATOMY : THE WINGS 481 



it may be brightly coloured, and in many of the species of Homoptera 

 is prolonged backwards over the abdomen in the form of a horn. 

 The meso- and metathorax are concealed under the scutellum and elytra, 

 and can only be seen by dissecting off these parts; their shape and size 

 varies in the different species. The scutellum is nearly always well 

 developed ; it may be prolonged into a sharp point or produced into a 

 broad process, when it conceals the wings. 



The exact number of abdominal segments is still a matter of dispute, 

 but as a rule eight can be clearly distinguished. In many of the 



Heteroptera, particularly among the species of the 



r -i V> * "j u i i LJ i The Abdomen 



family Reduvndae, the lateral abdominal margins are 



greatly developed, forming a plate-like expansion which is known as the 

 connexivum. In the genus Conorhinus this is well developed and is 

 especially conspicuous when the bug is in a starving condition ; most of 

 the species have coloured spots and stripes on the connexivum, which 

 are used as taxonomic characters (Plate LIX). 



The females in many species of the Heteroptera have relatively long 

 pointed ovipositors ; the external genitalia of the males are often very 

 conspicuous and have large claw-like claspers. During copulation the 

 sexes usually become firmly attached to each other, remaining so for a 

 considerable time. 



As is well-known most bugs emit strong offensive odours. The stink 

 glands of the adults are as a rule situated at the base of the abdomen, 



the ducts opening by means of an orifice on each side 



- Stink glands 



of the metasternum. In the larvae and nymphs the 



stink glands are situated on the dorsal surface of the abdomen and open 

 by ducts on each side of the mid-dorsal line. As a rule the plant 

 feeding Heteroptera have stink glands, while many of the predaceous 

 species are without them. 



The wings of bugs exhibit great diversity of form. There are two 

 pairs, the anterior of which are known as the elytra, hemielytra or 

 tegmina. Each hemielytron consists of a basal horny 

 portion and a membraneous apical part. In the 

 Heteroptera the basal part is divided into several distinct portions 

 separated by ridges. The corium (Plate LXII, fig. 8) forms the largest 

 part of the basal portion. Internal to it, and next to the scutellum 

 in the folded condition of the wing, is the clavus, which is often 

 sharply demarcated from the corium by a distinct ridge ; the outer and 

 costal part of the wing is called the embolium. In the family Capsidae 

 the apical part of the corium is separated off from the rest and is 

 61 



