84 Syrphidae. 



tarsi a similar pubescence on tlie pale parts, but darker on the dark 

 parts. Wings hyaline or a little yellowish on the basal half, brownish 

 on the apical half. this colour disappearing outwards so that a brown 

 median cloud is formed, defined inwards but not outwards; the cloud 

 may be more or less pronounced, sometimes very weakly. Stigma 

 blackish brown. Squamulæ whitish or brownish white with a darker 

 margin, the fringe whitish, sometimes brownish. Balteres likewise 

 dirty whitish to pale brownish. 



Female. Antennæ longer than in the male, third joint larger as it is 

 both longer and broader, but it is likewise slightly longer than broad. 

 Frons black, a little punctate, with distinct side dust spots; it is pale- 

 haired but in front of the ocelli and above and at the sides of the 

 antennæ the hairs are black; epistoma and occiput white-haired, the 

 latter shining above. Eyes with shorter and paler hairs than in the 

 male. Thorax with short, white pubescence. Pubescence on abdomen 

 whitish, but black at the incisures, the spots often larger and brighter 

 than in the male, but also here sometimes obscure and in rare cases 

 wanting. Legs pale-haired and the hairs only slightly shorter than in 

 the male. Wings generally with the cloud darker and more defined. 



Length. Somewhat varying, 6,5 — 10 mm. 



This species varies a good deal with regard to the abdominal 

 spots, and also else somewhat, but I think it may be known by the 

 spots, the cloud on the wings and the black epistomal pubescence in 

 the male. As seen it varies considerably in size; my largest specimens 

 are females, I think these answer to the form described as fenestrata 

 by Verrall (Brit. Fl. VIII, 171) considered by the author himself to be 

 a variety of noctiluca; two of these large females show a pair of small 

 linear spots on the third segment; I may also note, that I have not 

 rarely early in the season taken immature specimens in which almost 

 no wing-cloud is visible; these specimens often showed transl ucent 

 spots on third segment in both sexes; these spots seem later on to 

 disappear by pigmenting. — Among the synonyms from Zetterstedt 

 which I, foUowing the Kat. palåarkt. Dipt., have placed under this 

 species, some, f. inst. hijalipennis and stigmafica might perhaps Avith 

 more probability belong to bimaculata on account of the clear wings 

 and dark tarsi. Wahlgren (Entom. Tidskr. 1909. XIII, 15) piaces 

 hyalipennis as synonym to notata, which may perhaps be correct. 



F. noctiluca is not rare in Denmark; Ermelund, Dyrehaven, Lyngby 

 Mose, Fure Sø, Geel Skov, Hillerød, Tyvekrog, Nyrup Hegn, Egebæks 

 Vang. Nyraad near Vordingborg; on Lolland at Maribo an Nagelsti; 

 on Langeland at Lohals; on Funen at Veflinge and in Jutland in 

 Nørholm Skov at Varde, at Horsens and at Restrup near Aalborg; 



