EXTERNAL ANATOMY OF INSECTS. 711 



thick; in Staphylinus slender and long; in Aradus, Nepa, 

 &c, depressed and flat; compressed in Ophion and 

 Evania ; conical in Ccelyoxis; rhomboidal in many 

 Mantes; boat-shaped in many Lygcei; fusiform in various 

 Papilionidce ; lanceolate in some Ichneumonidce, falcate 

 in others ; nearly round in Diapria purpurascens ,• ovate 

 in Lyrops ; elliptical in Andrena ; oblong in many Xylo- 

 copcB; heart-shaped in the naked Euglossce; triangular 

 in Dytiscus; gibbous in Flata,- and vaulted in Chrysis. 

 At its base it is truncated in Sir ex ; retuse in most bees ; 

 forming the segment of a circle in Andrena; in general 

 sessile, but in the majority of Hymenoptera, as has been 

 already observed, terminating in a pedicle. The pedicle 

 is very short in the Andrenidce and Apidce ; long in the 

 Sphecidce ; thick in the Formicidce ; slender in Evania; 

 fusiform in Pelecinus ; clavate in Ammophila; campanu- 

 late in many Vespidce; nodose in Myrmica* ; squami- 

 gerous in Formica* : it sometimes also consists of two 

 joints, as in Ammophila and many Vespidce. As to 

 margin, some have none, as Centrotus ; in others, as 

 Dytiscus, it is very narrow; in others again, wide and 

 flat, as in the Nepida : in Staphylinus, Sec, it is distin- 

 guishable only on the upper side of the abdomen; in 

 Locusta Leach only on the under side, though mostly 

 intire ; it is serrated in Blatta, sinuated in Acanthia pa- 

 radoxa, and crenated in Cerceris. 



v. Proportions. These vary greatly in the different 

 tribes ; in some the abdomen is long and slender, as in 

 Locusta, and Staphylinus ; disproportionably so in a re- 

 markable degree in some Agrionidce from South America, 



- Plate IX. Fig. 18. /'. b Ibid. Fig. 17. H' . 



