836 M. W. R. de V. GRAHAM 



metanotum, but the latter is a small and variable structure, probably not a reliable 

 feature. The propodeal plicae (Langsfalten) form well-marked, convex ridges in 

 the syntypes of coeruleum ; in most of the types of umbratum they are weak, though 

 in one female just as distinct as in coeruleum. The other propodeal characters, the 

 colour of the legs, and the characters of the male metanotum and antennae, do not 

 hold good for all the syntypes of the respective species. In the female syntypes of 

 coeruleum the head and thorax are a bright blue-green ; in some of the syntypes of 

 umbratum these parts are dull blue-green, though in one female just as bright as in 

 coeruleum. 



In 1959 I captured a number of Pachyneuron, which I refer to umbratum, in 

 southern Sweden (Yddingen and Falsterbo). I feel certain that these all represent 

 only one species, yet they show considerable variation as regards size, colour of 

 body and legs, structure of the propodeum, and proportions of antennal segments 

 in the males. The smaller specimens exactly fit the types of umbratum, and some 

 of them are very close to the types of coeruleum, but differ in having the head and 

 thorax a duller blue-green, and in having the propodeal plicae weaker. Thus there 

 is just a slight doubt as to whether coeruleum is really the same as umbratum, although 

 the differences causing this dubiety are extremely small. 



The range of variation of umbratum (as observed in the syntypes and my Swedish 

 specimens) is as follows: 



$. Length 1-5-2-6 mm. Head and thorax varying from dull olive-green or bluish olive to 

 a fairly bright green or blue-green. Femora often more or less infuscate, sometimes wholly 

 pale ; tibiae pale, or with a fuscous subbasal ring, or (occasionally) mainly fuscous. Reticula- 

 tion of scutellar frenum finer in large specimens, coarse in small ones. Propodeal plicae varying 

 from very weak to quite distinct. Basal vein of fore wing usually with 2-9 hairs, occasionally 

 bare. 



o". Antenna with first funicular segment from 1-5 times to nearly twice as long as the pedi- 

 cellus, 1-6-2-3 times as long as broad, and approximately equal in length to, or very slightly 

 longer than, the sixth segment ; the latter 1-6-2 times as long as broad. Upper surface of 

 costal cell usually with a few hairs in its distal part. Head and thorax bright green to blue ; 

 legs (except coxae) yellow. 



Sweden, Holland, Switzerland, Czechoslovakia, Moldavian S.S.R. 



Biology. P. umbratum has been recorded as a parasite of Oscinella frit (L.) (Dipt., 

 Chloropidae) in Czechoslovakia (Secretariat, etc., 1966 : 120, 131), the material being 

 determined by Dr. Delucchi himself. Delucchi originally (19556 : 133) stated that 

 it has been reared in Lausanne from Syrphid pupae on willows. In late July and 

 early August, 1959, I captured a number of umbratum in Skane, Sweden, on foliage 

 of Salix cinerea L. at Falsterbo, and amongst reeds (Phragmites communis Trin.) at 

 Yddingen ; in the latter case I also reared some specimens from the puparia of an 

 undetermined Syrphid found on the leaves of these reeds. Imagines June- August. 



Pachyneuron formosum Walker 

 (Text-figs. 681, 682) 



Pachyneuron formosum Walker, 1833 : 380, o* ?■ 



Pachynevron speciosum [sic] Walker ; Blanchard, 1840 : 266 [lapsus']. 



