308 Tachinidae. 



sutural dorsocentrals, and three præ- and three postsutural acrosti- 

 chals; a præsutural intraalar bristle. Scutellum with four or some- 

 times only three marginal bristles on each side, the apical smaller or 

 larger, crossing. Three or four sternopleural bristles. Pteropleura 

 above with a couple of bristles. Abdomen ovate or more elongated 

 conical; excavation on second segment reaching hind margin. Ster- 

 nites concealed. There are only marginal bristles or third and fourth 

 segment also with discai bristles in various number; second segment 

 with marginal bristles, and fifth with bristles all over. Genitalia small, 

 more or less hidden; upper forceps more or less cleft in apical part 

 (at all events generally), a little longer than arms of lower forceps. 

 Legs with the bristles in the anterodorsal row on hind tibiæ more 

 or less unequal; claws and pulvilli in male more or less elongated; 

 front tarsi in female simple. Wings with first posterior cell more or 

 less narrowly open, sometimes very narrowly, ending somewhat 

 before to rather near apex of wing; discai angle rectangular or more 

 obtuse, apical cross-vein somewhat steep or more sloping, a little 

 concave or nearly straight; a quite small or no costal spine. 



The species are parasitic on Rhopalocera and Heterocera and 

 also on larvæ of Cimbicids and Tenthredinids ; affinis is known to 

 belong to Pantel's group 6; fimbriata and Westermanni to group 2 

 (Thompson 1923). 



The species of the genus Exorista belong to the most difficult 

 to discriminate safely; tliey are very nearly related to each other 

 in most cases, and many of them are very variable, also in such 

 characters as are generally used, as the relative length of the antennal 

 joints and the presence or absence of bristles on abdomen. This has 

 naturally caused a highly confused synonymy, and only in later 

 years a number of synonymicai questions has been settled, but still 

 much is to be done here. What has already been done shows that too 

 many species have been created. As seen in Kat. palåarkt. Dipt. a 

 great number of species have been described which cannot at all be 

 interpreted or with certainty referred to this genus. It is not possible 

 to give the number of European species, the said catalogue enumerates 

 some sixty, and even if not few of them are synonyms the number 

 is no doubt great. In Denmark 11 species have been found hitherto. 



I have kept the name Exorista for the genus, but strictly 

 Exorista Meig. 1903 with type larvarum should replace Tachina 

 of authors, and the present genus should have another name. 



