THEREVID.E 539 



and of tough consistency and show apparently nineteen segments ; 

 they are said to occur in fungi and rotten tree-trunks but I received a 

 female specimen of T. fwMlitata ? from Mr C. D. Ash, which he was con- 

 fident he had bred from a Lepidopterous larva, and also a male from Essex 

 (June 23, 1901) which had been bred from Triphm7ia interject a, which tends to 

 confirm Wahlberg's statement (Vet. Acad. Handl., 1838, ? ) that he had bred 

 T. cximia from Nortna larvpe ; Westwood also stated (Proc. Ent. Soc. Lond., 

 1859, 59) that the larvae had been bred from the pupne of Aleiicis pictaria 

 and S^jJiinx ligustri ; it is probable that the active young larvse live in loose 

 earth and sand and are ready to prey upon any vegetable or animal 

 refuse, or even to affix themselves to living larvae. 



This family is well defined and may be distinguished most readily from 

 the Bomhylidce by the presence of the small cross-vein and the five posterior 

 cells. It is hardly necessary to compare it with the eremochaetous Tahanidce 

 and Lcptidw, but it is desirable to give some distinctive cbaracters from 

 the Asilidcc and Ajjioccridw. The Asilidce are more heavily built pedestrian 

 predaceous flies with the eyes widely separated in both sexes and con- 

 spicuously bulging out from the depressed or even excavated vertical 

 portion of the frons ; their bristles are as a rule much more strongly 

 developed, the tarsal bristles being evidently used for grasping prey; the 

 subcostal vein is much longer and frequently (Laphrinw and Asilincv) 

 receives the radial vein before its tip. The Apioceridcc are easily dis- 

 tinguished by their spatulate palpi and their venation, the subcostal 

 vein being very long and receiving the radial vein and the upper branch 

 of the cubital fork (or both branches) before its tip, so that these veins 

 run upwards rather parallel to the wingmargin. 



The Thcrevidce are not a large family, about 250 species being 

 known which have been placed in rather more than a dozen imperfectly 

 distinguished genera ; they seem to occvn- in all parts of the world, though 

 the majority have been described from Europe and North America (about 

 seventy species from each) ; they are, however, apparently numerous in New 

 Zealand. In Britain we recognise about a dozen species, of which 1 have 

 seen only one {T. annulata) from Ireland, though Haliday recorded T. cincta 

 (probably nohilitata) from Holywood in Co. Down; liitherto our species 

 have been in a chaos of nomenclature for the reasons given by Loew in 

 1847, which are as true to-day as when he wrote them sixty years ago ; 

 Loew then said, " The genus Thcreva belongs to the Dipterous genera of 

 " our Fauna which quickly attract the eyes of the collector through their 

 " beauty; his first success in distinguishing them causes him no difficulty, 

 " partly because he at first possesses only universally common species, and 

 " partly because he applies no close criticism of the existing descriptions 

 " to the few species of his collection ; as soon as he enriches these, he 

 " must become doubtful about identifications which he had previously 

 " considered certain ; he notes that these descriptions apply to two or 

 " more closely allied species and does not know to which of these they 



