288 LEPTID^ 



near to but not touching tlie eyes ; quite behind the head there is long pale 

 pubescence. 



Thorax with much shorter pubescence, which causes the four pale lines 

 and the humeri to appear more conspicuously brownish yellow ; sternopleurte 

 with more abundant pubescence. 



Abdomen very distinct from that of the male, as there are no oi'ange 

 markings unless at the extreme tip, when viewed from above greyish black 

 with pale hindmargins to the four basal segments, but when viewed from 

 behind the ground colour is greyish yellow with a deep black band across the 

 foremargins of the live basal segments • on the two basal segments this black 

 band is wider but usually less defined than on the next three segments, but on 

 these three segments it dies away at the sides and is widened at the middle 

 down to the rather narrow yellowish grey hindmargin, and this hindmargin 

 is well defined about the middle but merges into the greyish yellow tinge of 

 the sides ; but sometimes these black bands are broader and extend more 

 towards the sides on especially the fourth and fifth segments, and a band is fairly 

 visible on the middle of the base of the sixth segment ; usually the sixth and 

 seventh segments are greyish yellow with indications against the foremargin 

 of very shallow black spots at the sides and at the middle of the sixth 

 segment. Pubescence brownish yellow, as long and as abundant as in the 

 male but more conspicuous because of the darker ground colour. Belly greyish 

 black, with the hindmargins rather obscurely yellowish grey; terminal 

 segments considerably withdrawn and the ovipositor almost concealed. 



Legs with the cox^e all greyish black ; posterior femora always paler than 

 in the darkened males, being entirely dull orange except when slightly 

 darkened beneath the basal half of the middle pair ; hind tibiae very 

 slightly longer than the tarsi ; " touch-hairs " beneath the front tarsi only 

 just perceptible. 



Length about 9 mm. 



This species is easily distinguished from A. marginata by its j)aler 

 legs ; A. picta Loew (from North Eussia to Siberia) is a very closely allied 

 species of which only the male is known, but that has darker pubescence on 

 the hinder part of the thorax and on the scutellum, an unspotted belly, and 

 much blacker legs, while the stigma is dark brown even to the tip of 

 the marginal cell. Loew also described a var. femoralis from Carinthia 

 which has the femora quite as dark as in the darkest English specimens, 

 but as our specimens vary so very much in this character I consider that 

 we can supply the intermediate forms with which he seems to have 

 been unacquainted ; the North American A. variegata is closely allied to 

 A. Ibis. 



A. Ibis has never occurred to me as a common species but I have 

 records from Devonshire (Avon Valley and Bickleigh), Sussex (Three 

 Bridges), Derbyshire (Matlock), Cheshire (Bowden), Monmouth (Wye 

 Valley), Brecknock (Hay), Northumljerland {t. Wingate), Perthshire 

 (Rannoch), Ayrshire (Barr), Kincardine (Banchory), Banff (Craigellachie), 

 Nairn, and Inverness (Spey Bridge), from May 27 to June 28. Its meta- 

 morphoses have often been recorded because the females have a remarkable 

 habit of bunching themselves together in large masses overhanging streams, 

 and thereby attracting notice to themselves. I have never seen one of these 

 bunches, but Walker said (Ins. Brit. Dipt., i., 70), "The female of this 

 " fly is gregarious, and attaches its eggs in large clusters to boughs hanging 

 " over streams, and there remains, and shortly dies. The cluster is generally 

 " pear-shaped, and sometimes contains many thousands of dead flies, and 

 " continually receives accessions by new comers settling upon it. When 

 " the larva is hatched it falls into the water, its future residence ; it has a 



