11. ISOPOGON 721 



of the underside of the posterior femora ; hind femora with numerous 

 comparatively short black bristly hairs beneath about the tip even on 

 the apical half ; front tibiai with about ten short black dorsal bristles, 

 six or eight conspicuous strong black postero-ventral bristles on the apical 

 half, and some long hairs on the underside, besides a short curved apical 

 thorn almost on the underside but twisted back ; middle tibiaj with about 

 eight black dorsal bristles, three long black antero-dorsal bristly hairs, three 

 or four long thin black hairs beneath, several long white antero- and postero- 

 ventral hairs and some short white postero-dorsal and posterior bristly hairs, 

 and several black apical bristles of which some short ones on the underside 

 are rather crowded ; hind tibise with about eight black (sometimes yellow) 

 postero-dorsal bristles on the whole length, three or four antero-dorsal of 

 which the lowest one (or sometimes all) may be white, and a rather dense 

 rigid black pubescence beneath the dilating part which is followed by 

 a shorter dense equal whitish ciliation all down to the tip ; the usual tiny 

 bristles on the basal half of the hind tibiai are rather sparse and black, but 

 those on the apical half are depressed whitish and more numerous so that 

 they cause posteriorly and beneath a silvery sheen ; anterior tarsi with the 

 usual circlets of black bristles, but the usual strong posterior bristle near the 

 base is rejjlaccd by several less conspicuous bristles and two anterior bristles 

 after the middle of the basal joint ; middle tarsi with two anterior bristles 

 on the basal joint not close to the base and no posterior bristle instead of the 

 usual single anterior and posterior bristle * ; hind tarsi with only very minute 

 black bristles at the tips of the last four joints, the basal joint having 

 abundant minute shimmering white pubescence and about six small black 

 plantar bristles on the cylindrical base; the second, third, and fourth joints 

 of the hind tarsi about equally short (being as short as broad), and the fifth 

 joint slightlj' dilated and rather long ovate, while the second and third joints 

 bear a slight dorsal continuance of the shimmering white pubescence. 

 Pulvilli brownish orange ; claws black. 



Wings faintly brownish and with the wing-tip sometimes conspicuously 

 brownish in mature specimens, or quite hyaline in juvenile specimens. Alar 

 squamae very narrow, brownish with a broad pale yellow or whitish margin 

 and a fairly abundant whitish fringe, Hal teres large, orange or yellow with 

 the stem brown. 



The following description of the female is made from a specimen 

 taken at Loch Maree on June 7, 1884, because it agrees well with 

 continental types and descriptions, but the more common British form is 

 mentioned later on. 



$ . Not much like the male, as it is a broader insect with stouter legs, simple 

 hind tarsi, and usually less hyaline wings. Head with the pale pubescence 

 less pure white and with no black hairs near the hindmargin of the eyes ; 

 frons considerably dusted about the sides. Palpi with long thin pale greyish 

 hairs ; Antenuce with the third joint apparently a little longer. 



Thorax with considerable greyish yellow pubescence anteriorly and 

 laterally but with that on the disc mainly black. 



Abdomen with the adherent pale pubescence slightly longer, less whitish, 

 and brushed more towards the tip ; the longer pubescence about the sides 

 near the base less whitish ; hind corners of the third, fourth, and fifth 

 segments with rather distinct patches of light grey dust, of which traces exist 

 on the second segment. Belly mth no trace of any black bristles on the 

 last segment. Ovipositor shining black and compressed, with a pair of ovate 

 terminal lamelke which are orange on the underside and which bear rather 

 long outstanding pale pubescence. 



Legs black, with the front tibiae distinctly reddish at the base, and the 

 middle tibiaj for more than the basal half, and the hind tibiae for more than 



* Almost all the Asilidie have one strong posterior bristle near the base of the front tarsi, one anterior 

 and one posterior near the base of the niiihUe tarsi, and one anterior near the base of the hind tarsi; 

 these bristles being probably used by all six legs in grasping prey, but the remarkable development of the 

 basal joint of the hind tarsi in the male of this species has apparently caused additional and diflisrent bristles 

 to be used on the anterior tarsi. 



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