210 STRATIOMYID^ 



Frons shining black with a slight bluish tinge, broad as it is fuUy one- 

 third the width of the head, minutely and sparsely punctate and hardly 

 widened at all until the obliquely striate eyemargins Avhich are level with a 

 slight undulating furrow crossing the frons a little above the antennae are 

 reached, but thence the space between the eyes very gradually widens down 

 to the mouth where it is less than half the width of the head ; l^oth frons and 

 face bear soft pale inconspicuous rather upturned pubescence ; upper part of 

 the back of the head puffed out behind the eyes so as to form a distinct 

 eye collar, but the lower part considerably more inflated. Eyes with much 

 shorter and rather sparser pubescence. Antennae hardly so long as the head ; 

 third joint slightly tapering. 



Thorax and scutellum bright greenish or bluish aeneous and bearing short 

 brownish yellow pubescence, which is depressed and rather abundant anteriorly 

 but which becomes rather longer and more erect on the back part and on the 

 scutellum and the scutellar spines ; front part of the disc rather densely 

 punctate but the punctuation gradually growing sparser until the hind part 

 is almost impunctate, while the disc of the scutellum is only sparsely 

 punctate ; the hind points of the humeri are yellowish, as is also a very 

 indistinct narrow line along the suture to the wing-base. 



Abdomen shining dark brownish black with a slight puri:»lish hue, and 

 bearing pale grey pubescence which is moderately long at the sides and which 

 extends widely on to the disc about the basal corners. 



Legs orange, being one colour from the trochanters to the base of the tarsi, 

 rather paler than in the male but not yellow as in B. Morrisii ; femora with 

 only short pubescence ; basal joint of the hind tarsi hardly dilated, as long- 

 as the other four joints together, and rather brownish orange but darkening 

 towards its tip. 



Wings pale brownish or with almost a blackish tinge, but yellowish at 

 the base ; stigma conspicuously dark brown. Alar squamae dull brownish 

 yellow. Halteres orange to yellow. 



Length about 5-5 mm. 



This species varies considerably in the tint of the colour of the legs, 

 which are however almost one colour from the trochanters to the tarsi (both 

 excluded) and that colour is not so blackish as in B. geniculata or B. 

 fiLScipcs nor so yellow as in B. Morrisii. B. geniculata has very much 

 blacker legs in both sexes, the basal joint of the hind tarsi longer and in 

 the male more equally dilated, the sidemarginal pubescence on the abdomen 

 of the male almost whitish instead of blackish, the halteres yellower, and 

 the frons of the female much narrower. B.f'uscipes differs in most respects 

 as in B. geniculata, but has the antennae shorter and the legs (especially in 

 the male) more similar to those of B. chalyheata. B. Morrisii cannot be con- 

 founded as the pale yellow legs in both sexes, the pale haired thorax of 

 the male, and the the narrow frons of the female at once distinguish it. 

 The shape of the flagellum of the antennae in B. chalyheata is distinct from 

 that in any of the allied species. 



B. chalyheata is one of the commonest and most widely distributed of 

 the British species of this genus, as I have very numerous localities from 

 Cornwall (Penzance) to Sutherland (Golspie, etc.), while Haliday recorded 

 it from near Belfast. The dates range from May 14 to June 26, so that it 

 appears to be an earlier species than its allies. It is recorded from North 

 and Middle Europe. Curtis stated that it had been bred from moss. 



Synonymy. — Forster described this species as British in 1771 (not 1781 as Loew 

 said) as Musca chalybata, obviously from a male, and consequently his name has 

 priority over Stratiomys sexdentata of Fabricius, which was also described from 

 England and obviously from a female. Meigen amended Forster's name in 1820 to 

 chalyheata, and a whole host of synonyms were sunk by Loew in 1846, with which 

 I agree except that B. JiavijMs Macq. and possibly B. obscura Meig. may be 



