INTRODUCTION. 5 



greatest development three in number. On the upper side they are 

 either invisible, or at most one or two (and then always the last one 

 or two) can be seen ; generally also on the underside only one or two 

 are visible. In form they are sometimes very like the last abdominal 

 segment, (occasionally the first genital segment is exactly similar as 

 in the before-mentioned Families, Capsina, AntJiocorida, &c.), and 

 they then appear as half or entire segments ; but sometimes they are 

 very dissimilar, and then they appear as distinct plates, but only 

 visible on the underside." 



The lateral margin of the abdominal segments is much developed 

 in several sections, and forms a flat, reflexed or vertical border to the 

 abdomen which is called the Connexivum. 



The Stigmata, or apertures by which air is admitted into the body, 

 are situated below the margins on each side of the under surface of 

 the body, viz., 1 between the pro- and mesosternum, 1 between the 

 meso- and metasternum, and 1 on each of the 6 abdominal segments. 

 There is also often a pair on the 2nd genital segment in the 2, or 

 on the 1st genital segment in the $ , where it assumes the form of an 

 abdominal segment. In Nepa the stigmata are wanting on all the 

 segments except the last. 



NATURAL HISTORY. 



It is probably in consequence of the fact that the Hemiptera- 

 Heteroptera are in all stages of their existence active and suctorial, 

 and the consequent difficulty of supplying them, in confinement, 

 with fresh, appropriate food, that but few observations upon their 

 natural history have been made or recorded. There is a gradual de- 

 velopment of the creature after it leaves the egg, not only in size but 

 in the perfection of its organs. The larva resembles the imago and 

 is said to cast its skin 3 times before it reaches the pupa state ; then 

 the insect is still more like the imago, but some of its parts, such as 

 the ocelli, wings and claws are either rudimentary, or are barely in- 

 dicated, and only become perfected after the last moult. But 



