8 LIFE HISTORY OF THE ALDER BLIGHT APHIS. 



whitish tinge; subcostal vein and the inner margin of the stigma 

 black ; oblique veins whitish, stigma short and broad, not angled at 

 the base of the stigmal vein, which starts from a little behind the 

 middle and is comparatively straight, thereby making the apical cell 

 rather narrow. Terminal distances between the veins subequal, that 

 between second discoidal and cubital somewhat greatest; basal one- 

 third of the cubitus hyaline, but not abortive, as it can usually be 

 traced to its base, which is very close to that of the second discoidal ; 

 bases of the two discoidals either approximate or quite contiguous; 

 discoidals of the hind wings proceeding connectedly from the sub- 

 costal vein. Larva with 5-jointed antenna? and the promuscis extend- 

 ing beyond tip of abdomen." 



Prof. Cyrus Thomas determined the alder blight as Schizoneura 

 tessellata, and gave the following short note concerning it : 



This species is found on the underside of the branches of the alder {AJnus 

 lubra), crowded together and concealed beneath a covering of snow-white down. 

 Wingless individuals, dull bluish-black ; the bacli of the segments are marlied 

 with strongly impressed lines and covered with white down in square, checker- 

 like spots. Length to tip of the abdomen, 0.16 inch. 



Prof. H. Osborn, on account of the simple venation of the wings, 

 referred the species to the genus Pemphigus. 



Lastly, it was described under the name of Pemphigus alni by the 

 Abbe L. Provancher, who supposed that it was a new species. The 

 following is an English translation of the French original descrip- 

 tion : 



Pemphigus of the alder. Pemphigus alni. 



Length, 0.8 mm. ; to the tip of the wings, 22 mm. Dark brown, including the 

 head and legs, covered entirely with a whitish powder. The abdomen is covered 

 with a long, white, and woolly secretion. The wings are transparent, the veins 

 brown and strong ; stigma elongated, narrow ; radical cell elongate, inferior 

 veins barely curved. 



Found in dense, compact masses, several inches long, on Alnus, during 

 September. 



Besides the above extracts pertaining to this species, it may be ap- 

 propriate to mention here also a short report by Dr. Peter Kalm, a 

 Swedish naturalist, of whose " Travels into North America " an Eng- 

 lish translation has been published. In Volume I, second edition 

 (1772), page 121, there is the following account of an insect on the 

 alder, noticed by him while traveling through Pennsylvania and 

 Delaware, October 3, 1748 : 



I saw to-day the Chermes of the alder (Chermes alni) in great abundance on 

 the branches of that tree, which for that reason looks quite white, and at a 

 distance api)ears as it were covered with mould. 



The above lines refer undoubtedly to P. tessellata, which Kalm 

 mistook for the European insect which was mentioned by Linnaeus 



