Tachinidae. 41 



according to the epistoma being narrower or broader. The ridges are 

 generally a little converging just below, sometimes rather strongly 

 to almost touching in the middle. The lower end of the ridges, from 

 which the margin of the mouth aperture bends off, is termed the 

 vibrissal angle. The middle part of epistoma lies somewhat sunken 

 between the ridges; often it has a more or less high longitudinal 

 middle keel, so that two antennal foveae are formed. The space 

 below the eyes to each side of the oral aperture is the jowl, which 

 may be from rather narrow to as broad (high) as the eye is high. 

 Between the ends of the cheeks, the eye, the jowls and the epistoma 

 there is a more or less triangular space (median R. D.) which I term 

 the intermediate triangle; it is less chitinised than the surrounding 

 parts. On the head we have the following bristles: a pair of ocellar 

 bristles on the ocellar triangle, rarely wanting; they are generally 

 directed forwards and more or less diverging, sometimes they are 

 directed upwards, backwards or outwards; they may vary consider- 

 ably in strength and in some cases they are stronger in female than 

 in male; a pair of inner and outer vertical bristles, the latter often 

 wanting in male, especially when the frons is narrowed; they are 

 rarely quite wanting; on the orbits along the frontal stripe there is 

 on each side a row of bristles, the frontal bristles; these rows stop at 

 the insertion of antennæ, or they stretch more or less down on the 

 cheeks, sometimes quite down, and this is of systematic importance; 

 the frontal bristles along the orbits are curved inwards and crossing; 

 the rows are generally a little diverging above, and one or some 

 (1- — 3) uppermost may be stronger, erect and reclinate, fmally the 

 uppermost may often be directed outwards either only in the female 

 or in both sexes; (this upper, often transverse bristle is generally 

 placed more outwards than the other frontals, it is the "soie pré- 

 verticale" Villeneuve). On the orbits, outside to the frontal bristles 

 there are generally two downwards directed bristles, the orbital 

 bristles; they are very often present only in female, but may also 

 be present in both sexes, especially when the front in the male is of 

 some breadth; rarely there is only one orbital bristle, or more than 

 two. On the vibrissal angle there is nearly always a specially strong 

 bristle, the large vibrissa; above it there is a number of smaller bristles, 

 the vibrissæ. The vibrissæ are of great systematic importance; some- 

 times there are none or only a couple above the large vibrissa, at 

 other times they may be more or less ascending to quite up, and they 

 may be finer or stronger. Below the vibrissæ, along the oral aperture 



