6. EUTOLMUS 665 



manner, and consequently he ultimately admitted that the distinctness of 

 the two <:onora was difficult to maintain, but (as has been noted under 

 DyHmacliu^) he gave the best characters he could find ; no difficulty can 

 arise between our British species, because D. Irigonus exhibits the thoracic 

 distinction very conspicuously when compared with E. rufiharhis. In 

 general it nuiy be accepted that any doubtful species which is large, or has 

 the legs with more reddish coloring than just the base of the tibiae is a 

 Eutolmus, and if a male has no projection from the middle of the hind- 

 margin of the eighth ventral segment it must be either a Eutolmus or a 

 Dysmachus but not a MacMmus ; the females of Machimus are easily 

 distinguished by the free anal lamellse, but it must be admitted that 

 there are a certain number of cases in which it is difficult to assign a 

 male to Dysmachus or Eutolmus, or to Eutohnus or Machimtis, and a female 

 to Dysmachus or Eutolmus. The distinctions are dealt with in more detail 

 under the description of the genus Dysmachus. 



Our British species of Eutolmus belongs to the group in which there 

 are no strong bristles beneath the front femora. Kather more than 

 twenty European species of the genus are well distinguished and eight or 

 ten others are more or less imperfectly known; the genus is otherwise 

 only doubtfully recorded from North America. 



1. E. rvilibarbis Meigen. Legs wholly blackish, and with ahnost all 

 their bristles black. 



A large fly which resembles P. alhiceps and M. rusticus, 



$ . Face moderately broad, gradually widening down to the niouth ; frons rather 

 abruptly arched out above the antennae but soon contracting to a narrower 

 widtli than the face, deeply sunk between the eyes on the upper part ; face 

 densely covered Avith didl yellow dust ; facial knob fairly large and well 

 defined, and the face-beard covering the lower two-thirds of the face but 

 • leaving the upjier third and the sides widely bare of pubescence ; hairs on 

 the middle part of the face-beard and along the sides of the mouth orange, but 

 those on the ujiper part and along the sides down to the upper angle of the 

 mouth black, and the black hairs down the sides are shorter and less con- 

 spicuous than the orange hairs on the middle part of the face-beard, while the 

 upper hairs hardly droop but the others droop more and more as they 

 approach the mouth ; chin- and jowl-beards quite distinct from the face-beard, 

 being closer, thinner-haired and denser, all orange and extending (though 

 becoming sparser) u}^ the back of the head ; on the upper part of the back of 

 the head the pubescence behind the black postocular festoon becomes slight 

 and is pale yellowish grey ; hindmargin of the eyes looped back a little at 

 about a quarter from the lowest part and with an apparently bare rather 

 wide pale greyish yellow postocular rim which becomes gradually wider on 

 the upper part and really bears a soft yellow pubescence ; postocular 

 festoon composed of about five well defined rather strong black bristles 

 on the upper quarter of the head, of which the uppermost are rather 

 bent forwards, while the festoon is continued downwards by about five 

 less strong and rather orange bristles which are less conspicuous and rather 

 bent downwards ; the uppermost black bristle of the festoon is level with the 

 top corner of the eye, and the actual postvertical channel is bare ; postocular 

 space with a slightly blackish elongate streak near the upper corner of each 

 eye ; irons covered with greyish or rather brownish yellow dust, but only 

 sparsely on the ocellar knob and on the middle part below ; several rather 

 irregular moderate bristly hairs occur on the widened sides of the frons 

 between the lower ocellus and the antennae, and about eight slightly longer 

 bristly hairs occur on the ocellar knob ; collar yellowish brown and bearing 



