12. XYLOMYIA 219 



because of its closed fourth posterior cell. The species are recorded from 

 Europe, North America, and South Asia. Their metamorphoses are well 

 known, and they are really far more common in the larval stage than in the 

 imaginal, as the habits of the perfect insects are very little known while 

 the larvae are easily found and easily reared ; I once however saw the 

 females of Xylomyia marginata running about the bark of some felled 

 trees in considerable numbers. 



Sj/nonym;/. — For a veiy long time this subfamily was included along with 

 Xylophagus in the family Xylophagidce, but is now considered to belong to the end 

 of the Siratiomyidce while the XylophagimjB are relegated to the beginning of the 

 Lepiklce. 



For the purposes of this work the subfamily may be considered to consist of only 

 the genera Xylomyia and possibly Rhachicerus, the latter being easily distinguished 

 by its remarkable antennae. Before any attempt is made to divide the genus 

 Xylomyia into those with simple and those with serrate hind femora a careful 

 examination should be made to find out upon what Walker's genus Solva was 

 founded. 



Table of the Faloiarctic Genera of XylomyintE. 



1 (2) Antennte with an eight-annulated simple flagelluui. Xylomyia. 



2 (1) Antennae with a multi-articulate (22 to 32), often pectinated, 



llagellum (fig. 166). Ehachicerus 



{Xylo^haginarwm ?). 



12. XYLOMYIA. 



Xylomyia Eondani, Dipt. Ital Prodr., iv., 11 (1861). 



Middle-sized to rather small almost bare flies, which are 

 mainly of black coloration with more or less yellow markings. 



Face and frons flush with the eyes or even slightly depressed ; face considerably 

 depressed on all the middle part except close to the antennse ; ocelli three. Proboscis 

 prominent, with small sucker-flaps; palpi two-jointed, cylindrical, rather long, 

 directed upwards and mainly lying upon the face. Eyes bare, well separated in the 

 male and still more widely separated in the female. Antennae (fig. 157) elongate,_as 

 long as or longer than the head ; two basal joints almost equal in length ; third 

 joint by far the longest, whip-shaped, composed of eight annulations of which 

 the first is the largest, and usually with a tiny apical bristle or style. 



Thorax short, oval, little arched ; pleurae with slight downy pubescence. 

 Scutellum without any marginal spines. 



Abdomen elongate, flattened, with seven distinct segments, but with no pro- 

 minent front angles. Genitalia of the male forming a large knob (? X. varia) 

 beneath the sixth and seventh dorsal segments ; ovipositor not protruded tubularly 

 but with a jiair of lamellae extending beyond the seventh dorsal segment. 



Legs rather long, almost bare and without any bristles ; front coxa3 long, but 

 not so long and cylindrical as in XylopJuuim ; posterior tibiae with two spurs each ; 

 coxai rather long. 



Wings (fig. 156) rather large, lying parallel on the abdomen when at rest, not 

 spotted ; costal vein extending after the end of the lower branch of the cubital fork 

 as an ambient vein to the end of the first or second veinlet from the discal cell ; 

 praef urea commencing well before the 1 lase of the discal cell ; cubital fork rather like 

 that of the Berime, being the longest and most wide open of any of the Stratimii/ido', 

 but differing from that of the Tkrime in being placed further out on the Aving and 

 just including the wing-tij) ; discal cell very difterent in shape from that of 

 any other palaearctic Stratiomyidce, being long and hexagonal as in the Leptidce, 



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