218 



STRATIOMYID^ 



two-thirds of the length of the upper basal cell • radial vein extended just beyond the 

 fork of the cubital ; cubital vein with a long fork, of which the lower branch ends in or 

 just after the tip of the wing, and the upper branch is fully two-thirds as long as 

 the lower one and ends about half-way between the radial vein and the wing-tip ; 

 basal cells all very long as they extend almost or quite to the middle of the wing, and 

 both (or, if including the anal cell, all three) nearly equally long ; discal cell distinctly 

 hexagonal with two short basal and two short end sides, remarkably long and dis- 

 tinct from the usual 8tratiomyid type, being about four times longer than broad, with 

 the upper and lower cross-veins placed at its basal sixth, and emitting three veinlets 

 of which the upper two, or only the upper one, extend completely to the wingmargin, 

 while the lower one bends sharply down and joins the upper branch of the postical 

 vein just before the wingmargin, and thereby forming a closed fourth posterior cell 

 which is peculiar to this subfamily in the Stratiomyidce ; postical vein with a long stem, 

 the stem being nearly twice as long as the whole upper branch, and with its fork simple, 

 but the upper branch is joined by the lowest veinlet from the discal cell just before 

 the wingmargin, while the lower branch is short and bends down rather abruptly 

 into the anal vein distinctly though not far before the wingmargin, and consequently 

 the fourth posterior cell and the anal cell are closed ; stem of the postical vein and 

 its lower branch strong ; anal vein (^uite reaching the wingmargin ; alula moderately 

 developed. Membrane of the wings minutely pubescent, but not at all ribbed, 

 though there may be slight inequalities or folds. Squamae very little developed, but 

 the alar pair present and slightly fringed especially at the lower angle ; thoracal 

 pair entirely absent. 



The Xylomyina3 are most allied in their venation to the Berina: in the 

 Stratiomyidm or to the jLylophaginoi in the Leptidce. They are dis- 



FlG. 154. — Xylomyia maculata S- "■< 10- 



Fig. 155. — Xylophagus aicr S. x 20. 



tinguished from the Xylo])hagin(€ as was pointed out by Osten Sacken by 

 the large prosternal plate which intervenes between the front coxse and the 

 anterior thoracic orifice {v. fig. 154), the comparatively short front coxae, and 

 the but little extensile abdominal segments, as well as by the closed fourth 

 posterior cell. They differ from all the other Stratiomyidm in the prsefurca 

 ( = common base of the radial and cubital veins) starting far before the 

 base of the discal cell, in the spurred posterior tibife (which otherwise only 

 occur on the middle tibise of Acanthomyia), in the closed fourth posterior 

 cell, and in the more extended ambient vein. 



The Xylomyincc comprise but very few species; in fact it is at present 

 uncertain whether they are not limited to the genus Xylomyia, although 

 probably one or two other genera which had been placed in the old family 

 Xyloj^hagidcv will ultimately be included and most likely Bhcuhicerus 



