1. XYLOPHAGUS 245 



Larv?e aiuphipneustic, allied to those of Cmnomyina: and Lc'ptiva\ 

 carnivorous, living under the bark of dead trees and preying upon other 

 (probably dead) larvse occurring there, especially those of wood-boring 

 Coleoptera, or upon the debris and detritus left by those larvse. 



This subfamily is divergent from the typical Leptidw in many ways, 

 and more especially in the long flagelliform annulated third joint of the 

 antennae ; it has this last character in common with the equally divergent 

 Ccenomyinm, from which it differs widely in the imaginal state though 

 allied in the larval stage. It seems to show more relationship to the 

 concluding subfamilies of the Stratioinyida:., and for a long time was 

 associated with Xylomyia in forming an intermediate family which was 

 called the Xylo^hcujidcc ; this old family differed from the Leptidcc in 

 having the third antennal joint annulated, and from the Stratiomyidcc in 

 having the tibise spurred, but subsequent investigations have proved that 

 those characters are misleading and a closer knowledge of the larvae has 

 proved that Xylomyia is a Stratiomyid somewhat allied to the Beri7icv 

 (some of which have spurred tibia?), while Xyhj2'>hagus is allied to the 

 Leptida:, towards which the perfect insect also shows connecting links in 

 its venation, its complete (though faint) ambient vein, its front coxse, its 

 prothorax, and its anatomy. 



The subfamily may possibly be limited to the genus Xylopihagus, but 

 if Rhachicerus be included it is distinguished by its remarkable antennse. 

 Fachystomus was founded upon a female specimen of Xylophagus cindus 

 with crumpled antennse. 



Only three Palsearctic species of Xylopliagus and one of Rhachicerus 

 are recognised. 



1. XYLOPHAGUS. 



Xylophagiis Meigen, Illig. Mag., ii., 266 (1803). 



Moderately large, almost bare, elongate, Ic//?ieumon-\ike 

 flies ; blackish colored but sometimes in tlie female with the 

 middle part of the abdomen considerably reddish. 



Head broader than high, as broad as the thorax. Face retreating. Vertex 

 rather drawn in so that the eyes appear rather swelled forward, and at no part does 

 the frons or face protrude beyond the level of the eyes, but there is sometimes an 

 antennal prominence. Proboscis prominent, with the moderately broad sucker- 

 flaps and the conspicuous keel-shaped two-jointed palpi directed upwards. Eyes 

 in both sexes separated almost equally from the vertex to the mouth ; facets all 

 almost equal. Antennae (figs. 180, 181) as long as or longer than the head; basal 

 joint sliglitly or considerably longer than the second : second joint short and 

 transverse; third joint ( = flagellum) longest, whip-shaped or cylindrical, with eight 

 annulations but with no terminal arista or style. 



_ Thorax rather elongate oval, little arched, almost bare, and without any sign of 

 bristles ; prothorax pubescent. Scutellum quite unarmed ; metanotum very large 

 and exposed. 



Abdomen of the male long and parallel-sided, quite twice as long as the thorax 

 and scutellum together, blunt at the tip, and with seven obvious segments ; _ of 

 the female less parallel-sided and much lengthened by the extended tube-like 

 telescopic ovipositor. 



