ISOCOLUS SCABIOS.E. 125 



respecting the images bis synopsis is certainly very elaborate, 

 — possibly more elaborate than clear, as tbere are many 

 gall-making species which I am unable to relegate to any of 

 his divisions; and, unfortunately for his successors, the 

 insect now under notice is made to serve as a type for two 

 widely-separated genera, — Isocolus and Euhothrus ; were it 

 a solitary instance it might possibly be accounted for by the 

 fact that Forster understood Giraud's species to include both 

 the gall-maker and the Aulax, a genus now divided, partly 

 inguilinous and partly gall-producing. The dwellers in the 

 galls of Rhodites and Diastrophus bear a most remarkable 

 resemblance to their hosts; in fact it requires great care to 

 distinguish them, differing as they do in many instances in 

 but a few secondary structural characters, the colorational 

 pattern being identical. However, this is not a note on 

 classification ; so suffice it to say that Scabiosce is very 

 properly separated from Diastrophus, but it is impossible to 

 give the characters concisely, Diastrophus is, as far as we 

 at present know, limited to gall-makers on Uuhus and the 

 allied Potentilla. Aulax is often an inmate in its galls, and 

 resembles it most closely, as has been said. We only have 

 one species in Britain, which galls the stems of the dewberry 

 {Ruhus ceesius) and its allies ; but our Potentilla gall, the 

 maker of which is now referable to Aulax, may possibly 

 have a closer relation : the inquiline has been described as 

 the maker of the gall more often than otherwise. Giraud's 

 diagnosis of our species is as follows : — " Niger, breviter 

 pubescens ; geniculis, tibiis tarsisque ferrugineis ; capite 

 thoraceque dense coriaceis, opacis; facie et pleuris aciculatis. 

 Areola nulla. Ant. mas 14, fern 13 art. Long, 2 — 3 mm." 

 (Verb. z.-b. Gesell.Wien. ix. 368). For the enlarged description 

 reference must be made. The specimen I have bred agrees 

 with his description, with the exception that the areola 

 (second cubital) is well defined, — he says, "areola nulla:" 

 this may point to the inquiline, of which, should I obtain 

 fresh galls and breed, I may have more to say hereafter ; as 

 it is, Giraud's description must be left as sufficiently correct. 

 The gall — which occurs on the leaf-stalk of the Ceniaurea 

 scahiosa, the species with the pinnalifid leaves — consists of 

 an irregular oviform swelling on the midrib, situate at the 

 base of the leaf, where it shoots forth froui the petiole ; it is but 



