STRATIOMYINtE 



127 



STRATI OMYINiE. 



Fig. 125.— Stratiomys potamida 9- X 4. 



Abdomen with only five or six obvious segments. Lower cross-vein 

 present ; discal cell emitting (normally) three faint, more or less incom- 

 plete, veinlets, and not emitting the upper branch of the postical vein ; 

 cubital fork short or absent. Antennae with no long thin arista. Scutellum 

 with two spines in the European species. Thoracal squamae large and 

 clothed with woolly pubescence. 



Antennae without any long apical or subapical bristle, but in Britisb species with 

 the third joint linear and annulated or club-shaped. 



Thorax squarely built ; metapleurse beset with dense shelter hairs. Scutellum 

 with two marginal spines in all the European species. 



Abdomen usually short and broad, often flattened, and with only five or six 

 apparent segments. 



Legs stout, moderate in length ; tibiae without any spurs. 



Wings with three veinlets issuing from the discal cell towards the wingmargin 

 and with five posterior cells, but the veinlets are often so faint or imperfect that 

 they can hardly be traced ; lower cross-vein distinct, so that 1 he postical vein is 

 quite clear of the discal cell and is only connected with it by the small cross- 

 vein ; cubital fork ending long before the tip of the wing and with the upper branch 

 short or even absent ; anal cell closed near the wingmargin • alula rather well 

 developed. Wing-membrane conspicuously ribbed or rippled radiatingly to the 

 wingmargin ; wings in repose incumbent and parallel on the broad flattened disc 

 of the abdomen but not covering the side-margins. Squamae distinct ; alar pair 

 comparatively small, and with a thick margin on which there is usually only a short 

 inconspicuous fringe ; thoracal pair large and conspicuous, semilunate or sub- 

 triangular {0. viridula), and clothed all over (on both the upper and under surfaces 

 and on a marginal fringe) with dense almost woolly, sometimes fuzzy, iDubescence. 



The metamorphoses of many species are well known, and the larvaj are some of 

 the " rat-tailed maggots " which occur in stagnant water. 



