Two New Shade-Tree Pests. 133 



this genus of sawflies. The females are provided with a saw-hke 

 ovipositor, shown in Fig. 27, with which their eggs are laid in the leaves. 



Historical Notes. — This insect was first described in Germany in 

 1846, but it is apparently not a pest and has attracted very little attention 

 in Europe.* Just when this sawfly miner was introduced into America 

 is not known ; but it was doubtless at least twenty years ago. For I found 

 it in injurious numbers at Newark and Ithaca in New York in 1891, and 

 the same year, Dr. James Fletcher, the Canadian entomologist, reported 

 a serious outbreak of what was probably the same insect, which " for 

 three years had entirely spoilt the appearance of the European alders 

 upon the grounds of the Experimental Farm at Ottawa'' (Can. Ent., 

 XXIII, 252). The insect was also reported as working on native alders 

 in a swamp near this Experimental Farm in 1893 (Can. Ent., XXV, 59, 

 by Harrington) ; and the same year an American alder, AIiius riigosa 

 (serrulata), at Woods' Holl, Mass., suffered seriously from this pest 

 (Can. Ent., XXV, 247, by Dyar). I have found no other references 

 to such an alder enemy in American literature. If it is the same species, 

 which is quite probable, that has been working on both European and 

 native alders in such widely separated localities from Massachusetts 

 through New York into Canada for ten years or more, doubtless it is 

 now widely distributed over this country. In Europe it is recorded as 

 working on Abuts glutinosa and incana; the former species in its many 

 varieties is now widely planted in America, and incana is the common 

 native alder along our northern streams. 



Its work. — The work of this alder sawfly is conspicuous and easily 

 recognized. It is well shown in Fig. 29. Small brown spots first appear 

 on the upper sides of the leaves where a single larva has begun its mine. 

 As the larvae feed and grow, the brown " blisters " increase in size and 

 often several of them join and form one large "blister" which may 

 involve nearly the whole leaf and contain 15 or 20 larvs. The mines are 

 just beneath the upper surface of the leaf which is thick enough so that 

 the work of the insect scarcely shows on the undersides of the leaves. 



Throughout the season, the infestation begins on the newest or 

 youngest leaves. Badly infested or " blistered " leaves die and drop off, 

 thus spoiling the ornamental effect of the trees, and checking their growth. 



According to Dalla Torre's Catalogue (1894), pp. 122 and 287, Lepeletier (Count of 

 St. Fargeau) described two sawflies as varipes, now placed in the genera Emphytus 

 and Priophorus. One of these is considered a variety of E. tibialis and the other 

 an aberration of P. padi. As neither of these species work on alder, it is at least 

 very doubtful if Harrington was correct in designating the species injuring alder in 

 Canada as Fcnusa varipes St. Fargeau (inclanopoda Cameron). 



*Apparently the only account in Europe of its life and habits is a paragraph by 

 Brische in 1883. (Beobach. Arten der Blattund Holzwespen, 2nd Abth., 261 (as 

 Fefmsa PhuiHq) in which the jif? and habits in late summer are briefly described, 



