18S7.1 57 



nearly bare ; tliorax testaceous and glabrous, showing the spur of a ■white central 

 ^tripe on its front margin, and having four bristles behind the suture in the outer 

 dorso-central row ; abdomen oval, yellow, and translucent, sometimes a little in- 

 fuscated on the back of the fourth and fifth segments, otherwise immaculate, edges 

 of the second and tliird segments destitute of bristles on the dorsum ; legs yellow, 

 with the exception of the tarsi, all the joints of which are black ; hind tibite of the 

 males with a strong black spur or spine projecting from their inner ends ; wings 

 with the external transverse veins rather oblique, and sometimes a little sinuous ; 

 the internal transverse vein is placed a little before the termination of the auxiliary 

 vein. 



P. SILACEA. — Frontal triangle in the male, as well as frontal space in the female, 

 yellow; eyes contiguous in the male, and quite bare ; face yellowish- white ; an- 

 tcnnte entirely yellow in the male, but with third joint black in the female ; arista 

 shortly ciliated, lengtli of hairs about the same as in the foi'mer species j thorax of a 

 dead whitish-yellow colovir, which is lighter at the fore part; unstriped ; bristles 

 in the dorso-central rows small, only three in the outer row behind the suture; ab- 

 domen small and flat, dull yellow, and when viewed in certain lights showing a wide 

 dorsal interrupted stripe* as well as transverse dark lines ; all the segments are 

 furnished with a thick even row of black bristles on their posterior edges ; legs 

 yellow, with the exception of the last four joints of the tarsi ; metatarsi pale ; there 

 is no spine on the inner extremity of the hind tibiae in the male ; wings, with the 

 external transverse veins very oblique in the male, so that they lie almost parallel 

 with the posterior borders of the wings, they are also very sinuous, being bent like 

 the letter S ; in the female these veins are much less oblique and sinuous than in 

 the male ; intei-nal transverse veins placed exactly opposite the termination of the 

 auxiliary vein. 



A comparison of the two descriptions will show that the species are widely 

 different, and that one is more highly developed than the other. Only knowing the 

 former when I published my list, I placed it in the genus Mydcea on account of the 

 shape of the abdomen and size of the alulets, &c. Prof. Mik thinks (hat it should 

 be classed among the Aricia {Ui/etodesice, Meade), on account of the slight hairyness 

 of the eyes, and he called my attention to the fact that H. Loew has described this 

 fly as a new species by the name of Aricia aculeata,f giving this specific name fi'om 

 its having tlie spurs on the hind tibia?. The almost nude state of the arista scarcely 

 fits this species to hold such a position, and in the present unsettled, and I may say 

 unsatisfactory, state of the generic distribution of the Anthomyiida:,X I think it will 

 be better to place both species provisionally in the genus Pe(jomyia,v;\niA\ is already 

 a very artificial group, including some species that are much more highly developed 

 than others, but have the abdomen and legs yellow. 



I will conclude these remarks with giving a sketch of what I believe to be the 

 correct synonymy of these species. 



* Meigen mentions this in his description of A. silacea, but it is omitted by Schiner ; who 

 says, however, that the abdomen shrinks up in drying and becou es short ; this probably caused 

 him to overlook the stripe. 



t Berl. Entora. Zeitschr., 1873, pp. 33—62. Diptera nova a F. Kowarzio capta. 



t M. J. Schiiabl, of War.saw, has lately published an elaborate memuir ujion the genus Aricia, 

 the scope of which he proposes greatly to enlarge. He considers the presence of hairs upon the 

 eyes an insufficient generic distinction. 



