Parasetigena. 357 



four times as long as second; arista with second joint a little elongated. 

 Thorax quadratic; foiir j30stsutural dorsocentrals, and three præ- 

 and three postsutural acrostichals; a præsutural intraalar bristle, 

 sometimes weak or wanting. Sciitellum with four marginal bristles 

 on each side, the apical somewhat small, erect and crossing. Three 

 sternopleural bristles. Pteropleura hairy, with a bristle above. Ab- 

 domen elongated conical; second segment with the excavation 

 reaching hind margin; only marginal bristles, on second segment 

 a pair. Legs with anterodorsal bristles on hind tibiæ uneqiial; claws 

 and pulvilli strongly elongated in male; front tarsi in female simple. 

 Wings with first posterior cell open, ending in some distance from 

 apex of wing; discai angle nearly rectangular; no costal spine. 



The biology is known for one species, the well known media 

 Rond. {segregata by Baer), which has as parasite on Lymantria monacha 

 been very important with regard to the destruction of this species, 

 and has been introduced to North America to attack L. dispar', it is 

 further recorded from some other Lepidoptera, but this is doubtful. 

 The records are upon the whole not sure, as the species has been 

 confused with P. segregata Rond. It belongs to Pantel's group 1 and 

 forms a primary breathing hole. One, rarely two parasites develop 

 in each host; they bore out of the host larva or pupa and pupates 

 in the ground, where they hibernate. 



Two or three European species are known, one occurring in 

 Denmark. 



1. P. media Rond. 



1859. Rond. Dipt. Ital. Prodr. III, 181, 6 (Chaetogena). — 1895. Pand. 

 Eev. Entom. XIV, 342, 17 {Zenillia). — 1906. Villen. Wien. Ent. Zeitg. XXV, 

 43 {Phorocera). — 1907. Villen. Ann. Soc. Ent. de Fr. LXXVI, 384. — 1907. 

 Kat. palåarkt. Dipt. III, 355 (Stomatomyia). — Phorocera segregata Schin. 

 (nec Rond.) F. A. I, 491. — 1893. B. B. Denkschr. Akad. Wiss. Wien, LX, 

 189, 51. — 1907. Villen. Wien. Ent. Zeitg. XXVI, 256, 49. — Phorocera agilis 

 1924. Stein, Arch. f. Naturgesch. 90, 6, 109. 



Male. Frons not fully as broad as the eye; cheeks very broad. 

 Orbits yellowish; cheeks yellowish white, silvery; jowls grey; frontal 

 stripe velvet black, Vibrissæ somewhat strong. Orbits and jowls 

 with black hairs. Occiput grey, with dense yellowish hairg and a row 

 of black hairs behind postocular bristles. Eyes densely pale-hairy. 

 Antennæ black; arista thickened in less than basal half. Palpi yellow, 

 darkened towards base. Thorax blackish, greyish pruinose, with 

 four black stripes, the median narrow, abbreviated behind; scutellum 



