1898.] 275 



OBSERVATIONS ON BBYOPSANTA DISTICSA. 

 BY G-. C. BIGNELL, P.E.S, 



For many years I have searched for this gall, believing I should 

 recognise it by Dr. Mayr's description, translated by Mr. Fitch in the 

 " Entomologist" for August, 1876, and also described and figured by 

 Cameron in the Eay Soc. Vol. for 1892. This year I collected what I 

 considered, at that time, galls of divisa, and from the upright sides I 

 thought they had been distorted by being inhabited by an inquiline or 

 parasite, but to my surprise and delight they proved to be those of 

 disticJia. 



The galls of disticha are very much like those of divisa, but can 

 be readily separated ; the former have their sides perpendicular, while 

 the latter are convex ; or, in other words, divisa is in form like an 

 orange, while that of disticha would be like an orange grown or forced 

 into a cylinder, to make its sides straight, but on the top there is an 

 umbilical depression, which is not present in divisa. 



In Cameron's description of the fly he says, not easily separated 

 from divisa ; in that species he describes the abdomen as black. Those 

 that I bred had the abdomen red, with a little black on the upper-side. 

 Seeing this, I sent a specimen to Mr. Fitch, who returned it, confirming 

 my opinion that it was disticha ; for a further confirmation I sent flies 

 and galls to Professor Kieffer of Bitsch, who in reply said the insects 

 agreed with his specimens, and the gall with the typical form of D. 

 disticha. 



The gall of disticha I have seen annually for many years, as I 

 mentioned at the commencement of this paper. I thought it was 

 divisa from its general appearance, but I always observed that they 

 were found singly, very seldom two on a leaf, and more often only a 

 single gall on the same tree, whereas divisa is generally found in some 

 numbers on a leaf, and occasionally in quantities sufficient to bend 

 down the branch. 



D. disticha occurs on the sapling oaks in Cann, Bickleigh and 

 other woods, covering many miles ; I think it must be generally dis- 

 tributed, for I have had about a dozen sent me to name from St. Issey, 

 Cornwall. 



The flies are difficult to obtain, as the galls are very much infested 

 with parasites. 



In the translation mentioned above it says, "The gall-fly is de- 

 veloped late in the autumn ; and, according to Von Schlechtendal, 

 leaves the gall in October and November; while Schenck gives spring 



