302 M. W. R. de V. GRAHAM 



Holotype $. England : Berkshire, Wytham Wood, 15.V.1952, on Salt x cinere a 

 L. (Graham), in Hope Department, University Museum, Oxford. 



Paratypes. Same locality as holotype, 1 $, 16. v. 1952, 1 $, 17.V.1952, both on 

 Salix cinerea L., 1 $, 30.V.1953 on sallow (probably S. cinerea L.), 1 $, 26.V.1954, 1 $, 

 13. v. 1959 (both on sallow) (all Graham) ; Buckinghamshire, Hell Coppice, near 

 Oakley, 1 <$, 31. v. 1953 (on sallow), 2 $, (on Salix cinerea) (Graham) ; Surrey, Effing- 

 ham, Barnthorns Wood, 1 $, bred i.vii.1942 from Rhabdophaga salicis (Schr.) on 

 Salix atrocinerea Brot. (= cinerea L.) (M. Niblett). One paratype <$ in Hope 

 Department, remainder^, $ in Graham collection. 



The SALICIS-Grovp 



Scutellum wholly reticulate, not noticeably more shiny than the mesoscutum ; the scutello- 

 axillar sutures converge strongly so as to approach the hind margin of the mesoscutum well 

 mesad of the hind ends of the notauli (Text-fig. 202), whilst anteriorly these grooved lines curve 

 round and meet so that the scutellum is separated from the mesoscutum by a deep, more or 

 less sculptured groove. Mesepimeron marked off from the mesepisternum by a distinct grooved 

 line or elongate fovea, not very elongate (about 1-5 to 2-5 times as long as broad). Propodeum 

 more or less alutaceous or reticulate, medially as long as or (usually) a little longer than the 

 scutellar frenum, its median carina nearly always more or less indicated, often complete though 

 sometimes irregular ; callus with two to seven hairs, but except in fulvicoxis sp. n., without 

 hairs above the supracoxal flange. Mesoscutum having its reticulation at least very slightly 

 raised above the general surface ; anteriorly the sculpture tends towards a transversely- 

 strigose or rippled type. Scutellar frenum distinctly marked off. Hind coxae usually with some 

 hairs dorsally, except in some very small specimens. Mesosternal mesolcus distinctly impressed. 

 Fore wing with marginal vein long, 2 to 2-3 times as long as the stigmal vein ; postmarginal 

 vein distinctly shorter than the marginal ; basal cell with some scattered hairs in its distal half 

 to two thirds, on the upper surface of the wing. Antennal scape shorter than an eye, not reach- 

 ing the median ocellus ; combined length of pedicellus and flagellum less than or at most barely 

 equal to the breadth of the head ; male flagellum clothed with relatively short bristles. 



Gaster of female not strongly compressed, ovate to lanceolate, with ovipositor sheaths at 

 most slightly projecting beyond the last tergite ; basal tergite usually with a subtriangular to 

 semicircular median depression at the base ; in most specimens of fulvicoxis sp. n., however, 

 there is a fovea on each side, separated by a convex ridge. 



Some of the taxa included here as distinct species have previously been regarded 

 as forms of one, salicis (Nees). It is possible, however, to segregate those dealt 

 with below fairly well on morphological characters. Their biology is too imperfectly 

 known as yet to provide useful information. All of them are apparently associated 

 with willows (Salix spp.) and the available breeding records refer to Rhabdophaga 

 spp. (Dipt., Cecidomyiidae) as hosts. At present it is difficult to assess how much 

 of the variation shown is due to host differences, to the same host on different 

 species of willow, or to geographical variation. As the Cecidomyiid hosts, and 

 sometimes the host willows, are by no means easy to determine, this is not surprising. 



A special study of the species of this group of Gastrancistrus would be a very 

 interesting and valuable contribution to our knowledge, which is at present rudi- 

 mentary. This can only be done by careful breeding from critically determined 

 hosts whose host willow species are accurately named. 





