ELM- TREE APHIDES. 277 



50. The cock's- comb elm gall- louse. 



Colopha ulmicola (Fitch). 



Order Hemiptera ; family Aphid^. 



The foJlowing account is taken from Professor Riley's Notes on the 

 Aphididse of the United States, published in Vol. V of the Bull. U. S. 

 Geol. and Geog. Survey : 



Forming cock's-comb-like galls on the upper surface of the leaves of Zflmus ameri- 

 cana, the galls appearing with the opening of the leaves, and turning brown and 

 black in late summer. A very common gall, which may be called the Cock's-comb 

 Elm Gall, being found on the White Elm, and particularly on young trees. It was 

 well described by Fitch as an " excresence or follicle like a cock's comb, arising ab- 

 ruptly on the upper side of the leaves, usually 1 inch long and one-fourth of an inch 

 high, compressed, its sides wrinkled perpendicularly and its summit irregularly 

 gashed and toothed ; of a paler green color than the leaf and more or less red on the 

 side exposed to the sun ; opening on the under side of the leaf by a long slit-like ori- 

 fice; inside wrinkled perpendicularly into deep plates." There are several genera- 

 tions and the sexual individuals are mouthless. I have not been able to prove abso- 

 lutely that there are two broods of the gall-making female, and my observations all 

 tend to the conclusion that no galls are formed except by the stem-mother that hatches 

 from the impregnated egg. There is a link wanting between the third generation 

 and the mouthless sexual individuals, but I am inclined to think that the third gen- 

 eration will be found to have a different habit, possibly feeding upon some other part 

 of the tree, without forming galls, and producing in time the true sexnal individaals. 



51. The wooly elm-tree louse. 



Schizoneura rileyi Thomas; Eriosoma ulmi (Riley). 



Order Hemiptera ; family Aphid^. 



Clustering on the limbs and trunks of the white elm, causing a knotty unnatural 

 growth of the wood ; small aphides covered with an intense white wool-like sub- 

 stance, the limbs at a distance appearing like snow. (Riley). 



In Illinois and Missouri, late in May and in June, the white elms in 

 the larger cities are apt to become infested with these conspicuous and 

 curious insects. Riley finds that by washing with a weak solution of 

 cresylic acid soap they will be instantly killed. 



The adult is dark blue, the wings clear, three times as long as wide, and more 

 pointed at the ends than in E. pyri. Costal and subcostal veins, and that bounding 

 the stigma behind, robust and black. Discoidal veins, together with the third forked 

 and stigmal veins, all slender and black, the forked vein being as distinct at its base 

 as are the others, with the fork but one-third as long as the vein itself and curved in 

 an opposite direction to the stigmal vein. Antennse 6-jointed and of the same color 

 as the body; joints 1,2, 4,5, and 6 of about equal length ; joint 3 thrice as long as 

 either. Legs of the same color as the body. Length to tip of closed wings, exclu- 

 sive of antennae, .12 inch. 



The young lice are narrower and usually lighter colored than the adults, varying 

 from flesh to various shades of blue and purple. 



52. Pulvinaria innumerabilis Rathvon. 



Mr. B. P. Mann reports {Pysche iv, 224) that he received from Au- 

 burn, N. Y., twigs of the elm bearing several mature specimens, with 



