Straliomyiidae. 75 



3. Body with slioit, somewhat depressed hairs 4. 



— Body with longer hairs, only the vential segments with shorter 



hairs in front O. argentata. 



4. Almost tlie whole dorsal and venlral suiface covered with 



short, depressed hairs O. tigrina. 



— The hairs on the ventral segments only occupying a somewhat 



narrow, transverse space in the middle, not quite depressed . . H. viridula. 



Xylophagidae. 



Head short, broader thaii liigli, as broad as thorax. Yowls very 

 narrow, not descending below the eyes; epistoiiia retreating. Antennæ 

 placed near to each other, in, or somewhat below, the middle of the 

 head, ten-jointed. Eyes bare, equally separated in both sexes, or the 

 front somewhat narrower in the male. Three oceili present. The part 

 of the head surrounding the mouth aperture not membranous, and 

 thus no oral cone is fornied; clypeus partly membranous, not distinctly 

 separated from the epistoma; proboscis short, the labella rather broad, 

 protruding forwards. Labrum of the length of the labium, hypopharynx 

 slightly shorter; maxillæ present, with a shorter or longer lacinia, and 

 two-jointed palpi. Thorax rectangular, scutelium unarmed, postscutelluni 

 rather large. Abdomen eiongated, consisting of seven segments. Legs 

 long, more or less slender, without bristles; all tibiæ with two apical 

 spurs (Xt/lopJiagus), or the spurs absent on the front tibiæ (Xylomyia). 

 Glaws simple; two pulvilli and a pulvilliform empodium. Wings with 

 the costal vein extending all round the margin, radial vein present, 

 cubital vein forked : the discai cell forrned exclusively of the discai vein, 

 connected with the postical vein by a postical cross-vein; five posterior 

 cells of which the fourth is open or closed ; the basal cells of equal 

 length and the anal cell almost or quite reaching the margin. Alula 

 absent (Xylophagus), or small f Xylomyia): alar squamulæ present but 

 small, thoracic squamulæ not developed, only the frenum present, bi 

 rest the wings lie parallel over the abdomen. 



The larvæ of the two genera are somewhat different, and I refer 

 with regard to tlieni to the genera. 



The Xylophagids are species of middle size and somewhat slender 

 form ; they occur in woods on or near hollow trees and trees or stubs 

 with otherwise decaying parts, and their larvæ live on such piaces. 



From the palæarctic region '.) species are known, and about three 

 times as many from North America : none are common to both regions. 



I am aquainted with no case of parasitic Hymenoptera on 

 Xylophagids. 



