18 STRATIOHYID^E. 



usual. Prsefurca originating in this family about opposite base 

 of discal cell (except in BEKINTE and XYLOMYIN.-E), whereas in all 

 other families of BRACHYCERA it originates much sooner. In 

 BERHNOE and XYLOMYINJE all the veins attain the wing-margin ;* 

 praefurca quite distinct ; costa nearly or quite reaching wing-tip ; 

 ambient vein more or less distinct: 4th posterior cell closed in 

 XYLOMYIN^E. In all subfamilies, membrane of wing always ribbed 

 or wrinkled ; squama variable in size, thoracic pair sometimes 

 absent. 



The STEATIOMYID^E are invariably bare of bristles or spines 

 (except the side thoracic spines in a few genera), but often possess 

 dense soft pubescence extending over the whole body and the 

 femora. The crowding together of the anterior veins and the 

 extremely wide variation of form in the antennae (perhaps greater 

 than in any other familv of Diptera) are their principal characters. 

 In the BERING and XYLOMYIN^E the venation takes the form of 

 the other allied families and the antenna? are more uniformly 

 constructed, elongate or subconical, with distinctly annulated 

 3rd joint. The family is closely allied to the LEPTID^E and 

 TABANID^ and to the small family of gigantic flies, the ACAN- 

 THOMERJD^:, known only from South America. 



Life-Mstory. The larvae show considerable variation, though 

 easily recognised when once seen, and those of some species are 

 popularly known as rat-tailed maggots, as are also those of the 

 ERISTALINYE. They are 12-segmented, including head, herni- 

 cephalous or conical, very elongate, rather leathery, and more or 

 less flattened. They live in earth, dung, semi-liquid or decaying 

 matter, and many are aquatic ; in the latter case the eggs are laid 

 on plants above the surface of the water. No pseudopods ; 

 terminal spiracles not visible, placed wholly inside a chamber 

 which has generally a closed or obscure aperture. Pupa coarctate, 

 in whicli character this family differs from all other BRACHYCERA, 

 the imago escaping through transverse slits on the 3rd and 5th 

 segment and a longitudinal slit between them. 



Many species hibernate in North Europe, but very possibly do 

 not do so in the Tropics. The life-histories of several European 

 species are well known. The imagines frequent grass and low 

 herbage in marshy situations and, generally speaking, are sluggish 

 in habits, though some have a very rapid flight in hot sunshiue.f 



Table of Subfamilies. 



1. Abdomen of at least seven obvious segments. ... 2. 

 Abdomen of five, or at most six, segments 3. 



2. Prsefurca beginning at about opposite base of 



discal cell ; 4th posterior cell wide open .... BERING, p. 89. 

 Prtefurca beginning considerably before base of [p. 96. 



discal cell ; 4th posterior cell closed XYI.OMYINJE, 



* Except for an abortive branch of the 4th vein in some BEHIND. 

 * Additional and more detailed information occurs under the various sub- 

 families or genera concerned. 



