DOLICHOPUS. 155 



sometimes long and pointed in the male ; the compressed tip often 

 slightly pellucid brown when the rest is black ; arista seated above, about 

 the middle of it, or nearer to the tip, finely pubescent or naked, the 

 penultimate joint extending beyond the third, but generally shorter than 

 the last, curved and forming a slight (or indistinct) angle with the last. 

 Scutellum usually flat and naked on the disc, sometimes slightly pubescent 

 (sp. 47-50). Metathoracic epimera larger than common, partly concealing 

 the sides of the first segment of the abdomen. Wings with the discal 

 transverse vein placed at about their half-length, its distance from the 

 hind margin (measured on the continuation of the pobrachial) more 

 than its own length ; praebrachial vein approaching the cubital towards 

 the end in a curve, or with a sudden twist, rarely forming two alter- 

 nate right angles with a rudimentary branch (sp. 35-37). The wings 

 often differ in the sexes ; the costal vein being thickened near its junc- 

 tion with the subcostal, or hind margin sinuated, or the markings 

 different, in the male.* The hairs which fringe the alulae are either 

 black or pale; in species 39-42 they have both black hairs and pale 

 pubescence. Abdomen conical, somewhat compressed behind; the 

 sixth segment in the male exserted, but short, glossy-tomentose with- 

 out bristles. Hypopygium long, somewhat compressed, darJc-coloured, 

 free, but scarcely petiolate, the seventh segment being very short : the 

 outer pair of appendages enlarged into plates, slightly concave, somewhat 

 like a bivalve shell, freely articulated by the narrow base, the margin 

 fringed and usually jagged at the end ; these, in conjunction with a 

 compressed lobe of each lateral margin of the hypopygium next the 

 belly, nearly conceal the other appendages excepting the uppermost one 

 (" aculeus ") ; but in some of those with unarmed metatarsi an exterior 

 forceps with slender arms is visible. In the species 39-42, which 

 Stannius has treated as a peculiar genus, Ammobates, the appendages are 

 singularly shaped, especially the aculeus, which is notched or toothed 

 and attenuated at the end into a curved spine. Each species has some 

 peculiarity in the form of these parts. The hind tibiae are rather 

 thickly spined ; in many also the hind metatarsus is spined ; and in a 

 few the posterior femora nave more than one spine towards the tip, 

 (these are liable to be broken off, but the sockets are visible as 

 black dots). In the males the tarsi are often peculiarly formed or 

 marked, or the femora fringed beneath, or the tibiae thickened, mostly 

 the hind pair, which have also a sort of variole in some (e. g., 

 sp. 17, 27). 



This extensive genus has obtained the particular attention of 

 authors. The admirable monograph by Stannius in the ( Isis ' for 

 1831, and that of the Danish species by Stseger, in Kroyer's 

 'Naturhist. Tidsskrift' (1842), deserve particular mention. 



* These distinctions have been minutely examined in most of the species, and 

 illustrated with figures, by Macquart in Ann. Soc. Ent. Fr. ser, 2. t. ii. pi. 4, 5. 



