232 [October, 



AYLAX ROGENHOFERI (WACHTL), A CYNIPID (HYMENOPTEEA) 

 NEW TO THE BRITISH FAUNA. 



BT ETCHARD S. BAGNALL, F.L.S. 



When I brought Aylax taraxaci forward in the September number 

 of this Magazine I scarcely thought that I should find it necessary to 

 record another species within such a short space of time. 



The gall of Aylax rogenhoferi is found in the heads of the 

 large knapweed {Centaurea scahiosa), and takes the farm of an ovoid 

 swelling, 3-6 mm. long by 2-3 mm. broad, generally situated at the 

 base of an imwlvcral bract on the inner face. The insect emerges 

 from the gall in the late spring of the second year. I have searched for 

 this gall on several occasions without success, but this afternoon, whilst 

 out with two geological friends, it was met with in plenty at two widely 

 separated localities. A few specimens were situated somewhat high up 

 the bract, instead of at the base. 



The deformation is not noticeable on the outer side of the head ; the 

 whole of the achenes of a flower, preferably dying, should be removed, 

 and a finger rubbed round the base of the inner side of the involucre, 

 when the swellings, if present, may be readily detected. The species is 

 also known to gall the achene of the same plant. 



Aylax rogenhoferi (Wachtl). 



Isocohis rogenlioferi Wachtl, 1880, Yerhandl. zool.-bot. Ges. 

 Wien, XXX, p. 542, pi. xviii, figs. 6-6 E. 



Hah. : Durham, Sunderland district, in quarries at Fulwell and 

 Ryhope respectively, Sept. 8th, 1917. 



Previously known from Central Em'ope, France, and Italy, 



I may add that I have, in the past, discovered old tenantless 

 workings of what I consider to be two other Cynipids, viz. of Aylax 

 jaceae and Phanacis centaureae, the former affecting the achenes and 

 the latter the stem of Centaurea nigra. Neither is known as British, 

 and search should be made for them ; on the Continent, both species 

 occur on several species of Centaurea. 



Penshaw Lodge, 



Penshaw, Co. Durham, 

 Sept. 8th, 1917. 



