1SC4.] 597 



inch. The diflFerence becomes still greater if we compare the average 

 <limensions of the gall found by myself on S. cordata. Again, Dr. Fitch 

 gives the length of the terminal bud or beak, which, as he correctly ob- 

 serves, is divided by 'a well-marked line of separation" from the rest 

 of the gall, as f of the length of the entire gall. In three freshly ga- 

 thered specimens from S. humilis, where the terminal bud is perfect 

 and uninjured, I find that it only averages .28 of the length of the en- 

 tire gall instead of .37 (=f), and I am satisfied that these three were 

 fair average specimens, from comparing them with those used in my 

 descriptions. On measuring Dr. Fitch's figure. I find that the bud is 

 .35 of the length of the entire gall, thus proving that the comparative 

 length of the bud, .37 or |, given in the text, cannot be typographically 

 erroneous. 



From the description of the larva as 9-jointed, it would appear that 

 Dr. Fitch considered the last bi-tuberculated or anal segment as a mere 

 anal process, and the three thoracic segments, (which in Cecidumyia 

 are never so clearly separated from each other as the abdominal seg- 

 ments, J as forming, together with the minute true head which is very 

 generally retracted, and which is no doubt the " slightly projecting 

 point" in the text, an enormous head or " head segment." bearing " near 

 the tip on the under side two small black lines," which are manifestly 

 the breast-bone. By thus deducting 4, viz : the anal and the three tho- 

 racic segments, from the real number of segmentvS. viz: 13, including 

 the head, we obtain the required number. 9. 



In the description of the imago there is nothing said as to the % 

 ( 9 ) antennae being pedicelled, but the figure, though rather rough, 

 represents them with pedicels about I as long as the joints, and the ver- 

 ticels about as long as two complete joints, just as in the S of all the 

 allied species. So near as I can guess at the number of joints in 9 an- 

 tennae of my species. I should say they are 21 (2-J-19) j but, as already 

 stated, I find it hard to count the joints of the $ antennae in the Willow 

 Cectdomyia with precision, from the terminal ones being so closely 

 united. The % of my species is unknown to me, so that I cannot com- 

 pare it with the S of the other form. Strictly speaking, as Dr. Fitch 

 gives "black" as the ground-color, and says nothing of the color of the 

 hairs of the thorax, they ought to be black, whereas in my species they 

 are grayish white. Probably, however, this was a mere oversight, or a 



