480 



DIPTERA 



CHAP. 



as sub-families. The Xylophaginae are a small group of slender 

 Insects, perhaps most like the short-bodied kinds of Asilidae ; 

 the third joint of the antenna is vaguely segmented, and there 

 is no terminal bristle. Rhachicerus is a most anomalous 

 little fly with rather long stiff antennae of an almost nemo- 

 cerous character, the segments of which give off a short 

 thick prolongation on each side, reminding one of a two-edged 

 saw. The three or four British species of Xylophaginae 

 are forest Insects, the larvae of which live under bark, and 

 are provided with a spear-like head with which they pierce 

 other Insects. The Coenomyiinae consist of the one genus 

 Coenomyia, with two or three European and Xorth American 

 species. They are remarkably thick-bodied, heavy flies, reminding 

 one somewhat of an imperfect Stratiomyid destitute of orna- 

 mentation. The metamorphosis of C. ferruginea has been 

 described by Bering. 1 The larva is not aquatic, but lives in 

 burrows or excavations in the earth where there are, or have 

 recently been, rotten logs ; it is probably predaceous. It is 

 cylindric, with an extremely small head and eleven other segments, 

 the stigma on the first thoracic segment distinct ; the terminal 

 segment is rather broad, and the structures surrounding the 

 stigma are complex. The pupa 

 has stigmata on each of ab- 

 dominal segments 2 to 8. Not- 

 withstanding that the fly is so 

 different to Xylophagus, the 

 larvae indicate the two forms 

 as perhaps really allied. One 

 of the Leptinae, Atltcrix ilns, 

 has a singular mode of ovi- 

 position (Fig. 227), the females 

 of the species deposit their eggs 

 in common, and, dying as they 

 do so, add their bodies to the 

 common mass, which becomes YiG.2-27.Atli?ri.vil>is. A, The fly, nnt. 

 an agglomeration, it may be size ; B, mass of dead flies overhanging 



water, much reduced. 



of thousands of individuals, and 



of considerable size. The mass is attached to a branch of a 



bush or to a plant overhanging water, into which it ulti- 



1 rcrh. Gcs. Wicn, xxx. 1880, p. 343. 



