192 TRANSACTIONS OF THE ILLINOIS 



to Eriosoma by Sir Oswald Mosley, and as the two appear to be distinct, 

 it is necessary to give this another specific name ; I have therefore named 

 it after the original describer. It is always preferable, where it is possible 

 to do so, to give these insects specific names, which indicate the plant on 

 which they feed, but in this case all the changes possible on the scientific 

 name of the elm have been rung ; two species, in fact, previous to this, 

 having received the name Aphis ulmi, the second by Ratzbu'rg, which has 

 since been transferred to Tetraueura. 



This species, which is quite common in this State, occasionally does 

 considerable injury to the white elms which are planted for shade or 

 ornament. They usually congregate in clusters on the limbs and trunk, 

 causing an unnatural and knotty growth of the wood, somewhat similar 

 to the knots produced on the roots of the apple tree by the preceding 

 species. Their habits, so far as observed, appear to be very similar to 

 those individuals of E. lanigera which inhabit the trunk of the apple 

 tree. 



The description given by Riley is as follows, which I give exactly as 

 he has given it, in order to afford the reader an opportunity of comparing 

 it with the description of the E. ulmi of Europe : 



Color, dark blue ; length to the tip of the closed wings, exclusive of 

 the antennee, 0.12 inch; wings, hyaline, three times as long as wide, and 

 more pointed at the end than E. pyri (^E. lanigera). Costal and sub- 

 costal 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 to its base as are the 

 others, with the fork about one-third as long as the vein itself and curved 

 in an opposite direction to the stigmal vein. Antennae, six-jointed, and 

 of the same color as the body; joints i, 2, 4 and 6 of about equal length, 

 joint 3 thrice as long as either. Legs of the same color as the body. The 

 young lice are narrower and usually lighter colored than the mature indi- 

 viduals, varying from flesh or pink to various shades of blue and purple. 

 The cottony or woolly secretion by these lice is very abundant, usually 

 covering them from view, and is very white. They generally appear in May 

 or early part of June, and by the latter part of June or first of July the 

 winged individuals are seen. Riley says that for these he has found by 

 experiment that a washing with a weak solution of cresylic soap will kill 

 them all instantly. He also adds that they are preyed upon unmercifully 

 by a species of lace-wing fly, which he names Chrysopa eriosoma. 



The characters of the Aphis ulmi, Linn., Erioso>na ulmi. Sir Os. Mos- 

 ley, are given as follows by Walker: Dull black; antenna stout, black, 

 moniliform, slightly setaceous, shorter than the body; abdomen very 

 short, slightly covered with gray filaments; legs moderately long; wings 

 colorless, very much longer than the body; wing-ribs, black ; stigma and 

 veins, brown ; stigma linear, rather long, acutely angular at each end ; 

 distance between the first and second veins at the tips full eight times 

 that between them at the base ; third vein nearer to the second towards 

 the base than at the tip, much nearer to the second at the tip than the 

 second is to the first. 



