11. ISOPOGON 719 



Isopogon is a small genus of probably only two Palaearctic species as I. 

 stjriacus Schin. is described as having bristles on the thorax ; one of these 

 is common over most of Europe, while the other is rare or but little 

 known. 



Synonymy. — The first name api^lied to this genus was tliat of Leptarthrua by 

 Stephens in his Catalogue of Britisli Insects (1829), but that was emphatically a 

 mere catalogue name, no distinctive characters whatever having been given except the 

 one conveyed in the word itself. Loew in 1847 declined to admit Stephens' name 

 on the ground that it was founded on a sexual character which applied to one 

 species only and substituted for it the name of Isopogon ; I cannot trace that even 

 this single sexual character was ever described by Stephens, or else I would use his 

 name because I consider Loew's action to have been very arbitrary ; Stephens in his 

 Illustrations (Vol. VII. Suppl., PI. xlv., 1846), when figuring Dasypogon diadema, 

 gave an adjoining figure which represents the hind tarsus of the male of his 

 LejHarfhrns, but I cannot trace that he ever gave the slightest indication of what 

 that figure was supposed to represent, so that no additional authority is given there 

 for the name. Loew in his turn committed a grave error in failing to notice the 

 curved thorn at the tip of the front tibige, but his genus is otherwise well defined ; 

 the result of this error was the formation of the genera Aphamartania Schin. 

 (1866), axid Pygostokisljw. (1866), which latter name being preoccupied was renamed 

 Nicodes by Jaennicke in 1867 ; it is possible that those genera may not be absolute 

 synonyms {Nicodes has a clubbed abdomen and an open anal cell, while 

 Aphamartania has bi'istles round the scutellum and a contracted first posterior 

 cell), but they were founded under the impression that Isopogon had no hook at the 

 end of the front tibiae. It is very remarkable that Schiner and others accepted and 

 described the genus wirhout detecting this error, but Brauer first called attention to 

 it in 1883 and then considered that Isopogon Lw. must sink under Aphamartania 

 Schin. because Loew had been in error in one character ( !), and that both names 

 were superseded by the catalogue name of Leptarthrus Steph., while Bezzi in Kertesz's 

 Katalog. der Palsearctischen Dipteren, II., 113 (1903) followed Brauer. 



1. I. brevirostris IMeigen. Hind tarsi of the male with the basal joint 

 very long and thin. Thorax with fairly long pubescence even to the front 

 part. 



The only British species of the Dasypogonince which is 

 entirely without bristles on any part of the thorax. 



$ . Black ; face moderately produced and arched, dusted grey except on a shining 

 middle space just below the antennse ; face-beard ^^black with the tips of 

 the hairs often bleached, hairs rather dense, equally long, drooping on the 

 lower part, and extending all over the face except quite close to (and on the 

 sides near) the antennae ; chin- and jowl-beards silky white and merging into 

 similar pubescence on the lower part of the back of the head, and the whole 

 of the rest of the back of the head away from the eyes with similar but longer 

 pubescence ; postocular margin broadly but rather indefinitely greyish white, 

 with sometimes some short black hairs close to the eyes on the lower part : 

 frons shorter than broad, deeply sunk between the eyes, shining black and 

 very little dusted, bearing long conspicuous black hairs on the orbits and still 

 longer black hairs on the ocellar prominence ; the sunk vertical space extends 

 quite bare down the middle of the back of the head ; collar small, black but 

 rendered dull bj'' dust, and bearing greyish white silky pubescence. Proboscis 

 black, rather shining, sloping forwards, and bearing short slight pubescence 

 about the tip but longer more abundant greyish white hairs beneath the basal 

 half ; palpi short, greyish black, and bearing long greyish white hairs. 

 Antenuje black ; two basal joints short cup-shaped and about equal in length, 

 both bearing black bristly hairs but those on the underside of the basal joint 

 long and occasionally to a large extent silky white ; third joint long and 

 narrow, quite bare, very slightly tapering and nearly twice as long as the two 



