1865.] 365 



and wish that, in the meantime, Mr. Bassett would describe the new 

 species.* 



Leaving aside, for the present, this intermediate and as yet doubtful 

 group, the following question requires, at this point, our attention. Are 

 all the Ci/nipidx of the second section of Hartig guest gall-flies or not ? 

 All the American gall-flies of the genera Synergus, Ceroptres and Au- 

 la. i\ which I have had the opportunity to observe, are guest gall-flies. 

 But Hartig and Griraud mention a number of Aulax, which they con- 

 sidered at true Psenides. This may really be the case, but before ad- 

 mitting it, we must advert to two circumstances, which may be sources 

 of error : 1. We have seen that Aulax ffierdcii, which is one of the 

 species said to be psenidous, is generically distinct from the other spe- 

 cies of Aulax ; Dr. Heinhard writes me that A. glechomse Htg., another 

 psenidous Aulax '-will probably have to be removed to the genus Dias- 

 trophus;" this proves, that the definition of Aulax by European authors 

 is more loose than that which we have adopted; may not all the gall- 

 producing Aulax of Hartig and Griraud belong to other genera? 2. 

 We have had frequent instances of inquilinous gall-flies erroneously 

 taken for the originators of the galls, and why could not the same error 

 have taken place with regard to certain species of Aulax ? I possess, 

 for instance, the European A. potent Mae, Villers, which is a true Aulax. 

 As the name implies, it is probably reared from a gall on Potentilla. 

 (I have not been able to compare the original reference.) Now, Mr. 

 Bassett has recently described a Diastrophus producing a gall on Po- 

 tentilla. Aulax, as we know, is frequently a guest of Rhodites and 

 Diastrophus; is it not possible that A. potentillx is likewise the guest 

 of a Diastrophus ? I am far from affirming that such is the case; my 

 purpose is merely to show how an error of this kind may originate. 

 The question whether Aulax is an entirely inquilinous genus, thus 

 remains as yet open. 



Genus AULAX. 

 Abdomen ( % ), with the segments 2 and 3 subequal in length, the 

 following somewhat projecting beyond the third; in the 9 the second 

 segment occupies nearly the whole surface of the abdomen and more or 

 less conceals the following segments. Antennae 14-jointed ( % ), and 

 12- (sometimes 13 ?) jointed ( 9 )• 



* Mr. Walsh has communicated me a gall-fly, which I cannot distinguish 

 from Mr. Bassett's gall-fly of Sinains, and which he bred from "'a woody sub- 

 spherical gall, surrounding a twig of Q. rubra." I merely state the fact, leav- 

 ing it for future observers to reconcile it with M. Bassett's statement. 



