658 ASILID^ 



(partly almost in a clump and partly extending down the light grey interstice), 

 about four (4-5 or rarely only 2) postalar, and numerous (up to 18) dorso-central ; 

 pteropleurae bristly or pubescent ; small prsealar callus (y. fig. 388) frequently 

 bristly ; metapleural fan composed of few bristles (about 5) or more numerous 

 bristly hairs (about 10) • hypopleural fan with about two long bristles or bristly 

 hairs besides some long hairs and pubescence, while some (1-3) bristles on the hind 

 coxae continue on in the same line as the two previous fans. Scutellum showing 

 great variation in the marginal bristles, as there may be numerous marginal hairs 

 of which a few (4-10) may be termed bristles or {D. spimfer) there may be two con- 

 spicuously strong bristles ; metanotum always with some short bristly hairs or 

 pubescence about its lower outer corners. 



Abdomen in our British species unusually short and conical (especially in the 

 female), but not so much so in the generality of species ; distinctly bristly, and with 

 more or less entire rows of pale praehindmarginal bristles on the segments ; eighth 

 ventral segment of the male neither widened, nor produced in any way, nor with a 

 pencil-like tuft of bristles, but frequently with a wide fringe of rather stiff hairs. 

 Genitalia hardly widened but sometimes very elongate (very short in our British 

 species) ; claspers and lower lamellae varying in shape, and both providing impor- 

 tant specific distinctions ; ovipositor (fig. 357) conspicuously laterally compressed 

 and with the eighth ventral segment prolonged so that the ovipositor is elongate- 

 triangular or peculiarly sabre-shaped when viewed sideways ; terminal lamellae 

 wedged in beneath the point of the upper piece as in Eutolmus. 



Legs black, or at most with the base of the tibiae inconspicuously rufescent, and 

 with the recumbent short pubescence somewhat obscuring them ; pubescence com- 

 paratively small in amount ; bristles perhaps rather more numerous than usual, 

 though usually absent beneath the front femora. 



Wings with a normal venation ; small cross-vein almost or quite punctiform. 

 Alar squamae strong on the basal part and with a thick margin. 



Loew originally included Dysmachus in Macquart's genus Lo'plionotus, 

 and distinguished it from other Asilince through the character of the 

 bristles on the middle stripe of the thorax extending to the front part ; 

 the distinctive generic character was founded upon the absence of a facial 

 knob in Loplionotus and its presence in Dysmachus. Subsequent discoveries 

 proved that the character of the bristles on the front part of the thorax 

 was not so good a distinction as had been originally believed, and in 1871 

 Loew (Beschr. eur. Dipt., ii., 142) wrote, "It is not quite easy to give a 

 " sharp boundary line between the particolored-legged species of Dysmaclius 

 " and EiLtohniLs. As all true species of Dysmachus agree with the species 

 " of Dutolmus in the position of the terminal lamellae of the ovipositor, the 

 " distinction of the two genera lies entirely in the difference of the bristling 

 " and pubescence on the disc of the thorax. In the typical species of 

 " Dysmachus the middle stripe of the thorax is beset with long hairs up to 

 " the front, and the bristles also extend to near the fore part ; in the 

 " typical species of Eutolmus the pubescence on the middle stripe of the 

 " thorax is short and the bristles are restricted to the hinder half of the 

 " disc. Outside these typical species however there is a whole row of 

 '■ intermediates upon the location of which there may well be uncertainty. 

 " These intermediates consist partly of those in which the pubescence is 

 " only very sparse or only short while the bristles extend far forward, or 

 " partly of those in which the pubescence has a notable length or great 

 " density while the bristles extend only to about the middle of the disc. 

 "If the two genera arc distinguished merely by the difference in the 

 " pubescence of the thorax, the boundary line between them is not only 

 " difficult to find but it separates the species in a manner but little 

 " corresponding to their mutual affinities. Altogether a rather natural 



