504 [December 



Imago. C. s. siliqua, n. sp.? 9 — Scarcely distinguishable either in 

 the recent or dried specimen from 9 'S'. rhodoides though the hair of 

 the thorax is not of so pale a white, as it is in C. s. strohiloidcs, C. s. 

 ;/naphah'oides, and C. s. rhodoides. Tn all the dried specimens, in- 

 deed, the legs are tinged with luteous. but so are they in several C. s. 

 hraxaicoides, C. s. strobihides, and C. s. rhodoides. The dimensions 

 are also about the same. From C s. hras^icoidei^ it diiFers in the 

 hair of the thorax being whitish, and from C. s. strohiloides in the 

 origin of the anterior branch of the 3rd longitudinal vein being pretty 

 distinct. From C. s. gnaphalioide.s it can scarcely be distinguished but 

 by its somewhat larger size, though it is possible that the % % may differ 

 in the average number of their antennal joints. Seven 9 .all bred from 

 the gall of S. humilis ; % unknown. From the slight but apparently 

 constant difference, in the galls found on S. humilis and S. cordata. I 

 incline to believe that we have here what I have called a Phytophagic 

 Species in an incipient state of formation. C. s. bra.s.'iicoides, C. s. 

 strobiloides, C. s. giiaphalioides, C .s. rhodoides and C s. cori/loides I 

 consider as well and long established Phytophagic Species, and that 

 the way it came about that there are two of them on one willow — S. 

 humilis — namely, the 3rd and 4th species, was, that they migrated ages 

 ago on to that willow from two other distinct species of willow, and 

 therefore, when they finally settled down on S. humilis, their gall-pro- 

 ducing secretions had different chemical properties, as we find to be the 

 case in Gt/nips q. spongifica 0. S. which is confined to the Black Oak. 

 and G. q. inanis 0. S. which is confined to the Red Oak, the two imagos 

 of these species being, as in so many Gecidomi/ia. utterly undistinguish- 

 able % 9 . 



As already stated, (p. 545) there is a gall (Salicis Fitch, =rigidae O. 

 S.) described by Dr. Fitch as growing upon S. rigida and S. lucida, 

 which seems identical with the above. Through the politeness of A. 

 Agassiz, Esq., I have been favored with a copy of Dr. Fitch's Article 

 on the subject, and also of his drawings, from the Quarterly Journal 

 of Agriculture and Science, Vol. I. p. 263. From these it results that 

 the two galls, so far as can be seen, are scarcely distinguishable; and 

 the same may be said of the larva and pupa as described by Dr. P'itch. As 

 regards the imago, he has manifestly — as appears both from the descrip- 

 tion and the figures of the anteunje. the joints of his % antenufe being 



