316 Orlhorrhapha brachycera. 



spines above; the last segment terminates with some hairs. The pupa 

 was resting in a cocoon, formed of particles of decaying wood, and 

 on the inside clothed with a thin film. Perris says in his description 

 of the pupa, about the first abdominal segment: "ayant de chaque 

 coté un trait corné, roux et arqué, atteignant le bord postérieur". 

 I find in the examined pupal skin exactly the same; the first ab- 

 dominal segment has on each side, somewhat above the side margin, 

 a reddish brown, curved, horn-like formation, issuing somewhat bchind 

 the front margin and reaching the posterior margin; but the horn is 

 lying on the inside of the skin, and I cannot say at present, wliat 

 it may be. 



According to what is said above the developmental stages, larva 

 and pupa, or only pupa, of seven species are known; they have all 

 been found under bark, and generally in company with Tomicins; it 

 may thus be considered as rather certain that the larvæ feed on the 

 larvæ and pupæ of Tomicins, as had been directly observed in two 

 cases; but probably they feed also on other larvæ found under the 

 bark, as stated by Kleine. The larva forms, before pupation, a cocoon 

 of some silky substance, to which is, or is not, added particles of the 

 surrounding matler. 



The species of Medeterus are very characteristic flies; they occnr 

 on tree-trunks, walls, boardings and the like, generally in great numbers, 

 some seem especially to occur on stones. They sit in a very charac- 

 teristic fashion, with the head and front part of the body in an up- 

 right position, and they move in a very curious manner, running side- 

 wards, backwards and in every direction without turning; they run 

 swiftly, and when chased they fly only a short distance. They are 

 perhaps the most strong robbers among the Dolichopodids, as also 

 indicated by their very strong mouth. I have however never observed 

 any of them with prey, but there are rnany records of it; already 

 Fischer de Waldheim observed that M. diadema lived on small insects, 

 especially Psychoda phalaetioides ; Schiner and Kowarz note that they 

 are strong robbers; Zetterstedt says about M. diadema (rostratiis) 

 ''Diptera minora prædans", and Poulton records (Trans, Ent. Soc. 

 London, 1906, 391) M. truncorum with a small species of Collemhola 

 {Degeeria cincta Lubb.?) as prey; also Kleine mentions (Berl. Ent. 

 Zeitschr. 1. c.) M. obscurus as rapacious and says that it hangs on the 

 low^er side of leaves, spying for prey, and he continues: "Alles was 

 nur einigermassen zu bezwingen ist fållt diesem kiihnen Råuber zum 

 Opfer". Finally Mr. Kryger told me that he has observed M. trun- 

 corum chasing and devouring Aphids. 



