546 [December 



great abundance, with the single exception of the first, which is exceed- 

 ingly rare, are named by Mr. Bebb as follows : — 1st. Salix discolor Muhl. 

 2nd. S. cordata Muhl. Srd. S. longifolia Muhl. 4th. S. nigra Mar- 

 shall. 5th. S. humilis Marshall. The first species produces one very 

 distinct gall. No. 6, and two that are apparently identical with Nos. 8 & 

 12, which occur on S. humilis. The second produces four very distinct 

 galls, Nos. 2, 10, 17 & 20, besides varieties of the very same two galls, 

 Nos. 8 & 12, of which varieties occur on S. discolor. The third three 

 galls, Nos. 1, 9 & 19. The/owr^/i two galls, Nos. 14 & 15. And the 

 fifth and last the astonishing number often distinct galls, Nos. 4, 5, 7, 

 8, 11, 12, 13, 16, 18 & 21. Mr. Bebb observes that " the tendency of 

 this species to produce a remarkable number of galls was observed by 

 Muhlenberg, and he therefore called it S. conifera." Besides the above. 

 I have also described a gall (No. 3) growing on S. rostrata, a northern 

 species which does not occur so far south as Rock Island, and a coleop- 

 terous gall or rather pseudo-gall, (No. 22,) which grows on S. longi- 

 folia, and also, so far as can be judged from the gall alone, on a 

 species of the allied genus Populus, P. angulata the common cotton- 

 wood. In addition to the five species of willow catalogued above, I 

 noticed in the woods a single large tree of what I believe is a sixth 

 distinct species, but too late in the season to obtain specimens of the 

 inflorescence. From the foliage and a portion of the fruit forwarded 

 to Mr. Bebb, he decides that it must be either S. nigra, which I am 

 pretty sure it is not, or some foreign species. Since however this tree 

 bore no galls whatever, the question, in an entomological point of view, 

 is of no manner of interest, except so far as it may illustrate what I rather 

 believe to be a general law, that exotic willows bear no galls. So far as 

 my very limited observation goes, exotic Willows (S. babylonica and S. 

 alba) bear no galls at all ; which is collateral proof of the theory, that 

 generally each distinct gall is peculiar to a distinct species of Willow, 

 for if it had been otherwise, the indigenous gall-makers would have 

 immediately attacked them when they were imported. 



Of the above twenty-one galls, excluding the Coleopterous pseudo- 

 gall and the doubtful galls on S. discolor and S. cordata, twelve (Nos. 

 1-15) are made by Dipterous insects belonging to the family (pA-idomj/- 

 idae, and six (Nos. 16 — 21) by Hymenopterous insects belonging to the 

 family Tenthredlnidse. In addition to a great number of insects which 



