1. PACHYGASTER 



1 1 



" les tibias ont aussi un pen de brim vers leur base." This description at once 

 excludes P. atra and P. LeacMi, both of which were well known to Diifour, and 

 it maybe concluded that it excludes P. mmw^mj'ma ; it is therefore limited to 7'. 

 tarsalis and P. orbitalls ; Loew, in ado])ting the name, was evidently influenced by 

 the words " alis immaculatis '' and by the type specimen which he possessed, but in 

 bred or immature specimens of P. tarsalis, especially when the wings are folded, the 

 ilarker base of the wing becomes very vague, and I think I can prove that the type 

 specimens are valueless ; further, close examination of Dufour's description notes 

 the words '' nervis a basi ad medium atris antennis rufo-fuscis " which apply better 

 to P. tarsalis, and most fatal is " les tiljias ont aussi un pen de brun vers leur base,'"' 

 a cliaracter which essentially does not apply to P. orhitalis, but does apply to P. 

 tarsalis more than to -any other European species of P achy cj aster ; beyond this I am 

 impressed by the omissions in Dufour's description, sucli as the silvery orbits, the 

 whitish halteres, and the broad frons of the male, which are characters that I believe 

 could not have been overlooked ; I am also impressed with the food-plant, as we 

 have evidence that /-*. tarsalis breeds in Poplar, while P. orhitalis seems to have a 

 very strong partiality for Holly. Dufour's hgure of the larva of P. meromelas favours 

 P. tarsalis, luit his description of the pupa agrees with P. orbitalis. As to type 

 specimens. Bigot was much better off than Loew as he possessed four against Loew's 

 one ; the two specimens above the label " P. meromelas S Landes L. Duf (nomt^.) " 

 are on one pin and are accompanied by a pupa case (fig. 100), and are both P. 

 tarsalis (^ ; the two labelled 'P . meromelas ? Landes L. Duf (nom*.) " are also on 

 one pin, the lower one being P. tarsalis $ and the upper one either a remarkable 

 variety of P. orbitalis $ or an undescribed species which I have noticed in my 

 remarks above. Under these circumstances I consider that Dufour's P. meromelas 

 cannot be recognised either from description or fi-om known types, and that at any 

 rate it cannot be accepted as the name for the species now under discussion, and 

 that it is equally certain that the male of Jaennicke's P. argentifer and Loew's P. 

 orbitalis do not belong to this species but probably to P. tarsalis. Loew, in 1872, 

 suggested that this species might be the Nemotelus frontalis of Olivier, Encycl! 

 meth., viii., 184 (1811), but I cannot help believing that Olivier's species referred to 

 Xemotelus nigrinm, especially as he seems to have fully recognised the characters of 

 the gQmxfi Nemotelus. It is also suggested that Fallen had this species mixed u]) 

 \v\t\\\\\A Sargus jKichygaster, because he notes, "Alae vel hyalinae vel saepius ad 

 basin dimidiato-nigrae : — Halteres all;)i." 



5. P. Leachii Curtis. Wings without any blackish hue on the basai 

 half. Legs yellow with only a blackish ring near the tip of the hind 

 femora. 



A neat shining black species with hyaline wings and pale 

 yellow femora. 



rj . Head in protile quite as long as high, 1 nit not circular because the front part 

 bulges out and the hind part is flattened. Face and frons forming a very 

 small shining black triangle when viewed from in front, but, as the under side 

 of the head is very much flattened, the face when viewed from below is not so 

 very small and bears some very short pubescence ; frons quite bare ; jowls 

 very small, shining black ; back of the head shining black and slightly puffed 

 out on the lower part but disappearing higher up behind the eyes ; vertex 

 shining black and bare, very long, narrow and pointed as it extends half way 

 from the occiput to the antennae ; ocelli slightly raised and with minute dark 

 pubescence behind ; proboscis brownish yellow. Eyes very nearly bare, 

 touching for about one-third (but below the middle) of the distance between 

 the occiput and the antennae ; facets on the upper part larger than those 

 on the lower part, but without any distinct contrast ; in life they are 

 reddish broAvn on the large facets and dark lirown on the small facets, but 

 withoiit_ much contrast in colour. Antennae orange, but with the two small 

 basal joints blackish or at least brownish and l^earing tiny bristles beneatli ; 

 arista long, thin, whitish yellow, rather densely but so minutely pubescent 

 as to appear merely slightly thickened except at the tip. 



Thorax shining black, thickly but not coarsely imnctate in front of the 



