Helicobosca. . 509 



short. Thorax a little rectangular; four postsutural dorsocentrals, 

 two or three præ- and postsutural acrostichals ; no præsutural in- 

 traalar bristle. Scutellum as a rule with five marginal bristles on 

 each side the apical strong, crossing. Four sternopleural bristles. 

 Pteropleura above with a small bristle in a bunch of hairs. Pro- 

 pleura hairy. Abdomen conical; excavation on second segment 

 reaching hind margin ; there are only marginal bristles, none on second 

 segment. Legs with rather long bristles; claws and pulvilH in male 

 elongated (distinguenda) or about equal in both sexes (muscaria) ; 

 front tarsi in female simple. Wings with first posterior cell open, 

 ending a little before apex of wing; discai angle rectangular, with 

 indication of a veinlet; posterior cross- vein rather near the angle; 

 no costal spine. 



The species have a pecuhar development; my specimens of 

 distinguenda are bred from Helix hortensis, so that the way of develop- 

 ment of this species is sure; muscaria is recorded as bred from H. ar- 

 bustorum, pisana and pomatia, but as the synonymy is at present 

 uncertain it is doubtful to which of the two species the recorded 

 observations belong; probably both live in the same way. They are 

 not parasitic but feed on dead snails (see Schmitz: Biol. Zentralbl. 

 37, 1917, 27). The female is viviparous and deposits a larva of a 

 size of 5 mm on a dead snail; the larva goes generally in the gro und 

 to pupate, but may also be found in the snailshell, and it generally 

 hibernates as pupa. 



Of the genus two European species are known, one has hitherto 

 been found in Denmark. 



1. H. distinguenda Villen. 

 1924. Villen. Ann. des Se. Nat. 10, VII, 35. 



Male. Frons about half as broad as the eye; cheeks narrow. 

 Orbits greyish white, darker upwards, cheeks silvery; jowls grey, 

 intermediate triangle red in certain views; frontal stripe brownish, 

 seen from in front white pruinose. Orbits black-haired; cheeks with 

 a row of small hairs and below with three strong bristles; jowls with 

 long, black hairs. Occiput grey, with black hairs. Antennæ black, 

 third joint somewhat dilated; arista long, thickened in basal half 

 but evenly tapering, short-hairy in basal half. Palpi yellow. Thorax 

 black, grey pruinose, with three broad black stripes, the median 

 abbreviated behind and with a narrow stripe on each side. Thorax 



