168 STR AXIOM YID^ 



Four well-distinguislied fairly common species occur in Britain, viz., *S'. hi^mnctatus 

 Jlavipes, cuprarius, and iridatus, but other forms occur which will not satisfactorily 

 agree with any of these. aS'. albibarhus 1 is certainly distinct from any other British 

 species (unless it should prove to be the true male of S. rnfipes) but is only known 

 from one or two certain European specimens. *S'. rnfipes is very close to S. flavipes, 

 and may not be the species distinguished by Wahlberg, or I may have incorrectly 

 recognised the male. H. nitidus must belong to the same group because of the 

 absence of the characteristic outstanding postocular fringe, but it may be a very 

 black form of S. flavijns unless the female prove to be black legged. S. minimus is 

 an eminently unsatisfactory species of which very few specimens are known, but at 

 present it cannot possibly be allocated to any of ihe others. S. nubecidosus has been 

 generally considered a small dark variety of aS'. cuprm-ius, but if the character of the 

 black postocular fringe of the male prove constant it is probably a good species. 

 The five doubtful species have never been adequately described by previous writers, 

 and have apparently never been taken in numbers in both sexes. 



1. S. bipunctatus Scopoli. Legs all orange in both sexes. Abdomen 

 of the male with some short golden orange pubescence on the disc, and of 

 the female with extensive orange markings about the base. 



A handsome green species of which the female is one 

 of our most beautiful British flies. 



$ . Frons (figs, 136, 138) shining blue-black or green, but blackish all about the 

 ocelli, narrow at the top and gradually narrowing to below the ocelli, after which 

 it gradually widens down to the antennae where it is about twice as wide as at 

 the top ; front ocellus not quite so near the upper two as they are to each other; 

 the raised vertex and ocellar space are practically at the top of the head, and 

 when seen in profile they occupy about the top quarter of the frons : lower 



half of the frons only very slightly raised above 

 the level of the eyes, sj)arsely punctate at the sides 

 and bearing there upturned blackish pubescence, 

 but impunctate and bare on a middle line which 

 begins narrowly some distance after the ocelli and 

 thence widens as the frons widens ; the actual 

 occiput between the eyes bears long rather dense 

 brownish yellow pubescence, but as soon as the 

 space between the eyes begins to contract the 

 pubescence is less long and is darker brownish 

 and all pointing forwards, becoming black towards 

 Fig. 138.— s. &i?)Mwc<a«Ms (J. the end of the ocellar sjiace and separated by 

 ^ 12. a short interval from the upturned frontal 



pubescence ; there is a pair of conspicuous white 

 spots on the forepart of the frons a little above the antennae and close 

 against the eyes. Face rounded and a little produced, greenish blue, 

 and bearing a rather long and moderately dense pubescence which is 

 black near the antennae and brownish below, and this pubescence is 

 upturned on the disc of the face but is drooping downwards on the upper 

 part of the sides against the eyes and is continued (but brownish yellow) 

 down the sides of the mouth ; jowls narrow, with greyish yellow pendent 

 pubescence continued in a narrow line under the eyes to the shorter pale 

 pubescence on the lower quarter of the back of the head ^ the rest of the 

 back of the head is hollowed and shows only microscopical pubescence ; 

 proboscis orange, with rather large sucker-flaps. Eyes bare, distinctly 

 separated all down the frons ; facets large on the prominent front part even 

 up to the inner sides, but gradually diminishing in size behind and especially 

 on all the lower part. Antennae dull black ; basal joint rather cylindrical 

 though short ; second joint rather shorter and cup-shaped, and both the 

 basal joints bearing rather dense short black bristly hairs ; third joint bare, 

 rather longer than the basal joint, and with four annulations of which the 

 last one is the smallest in bulk and bears at its extreme dorsal base the long 



