€o Bulletin 233. 



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 n^a'r this Experimental Farm in 1893 

 (Can. Ent., XXV, 59, by Harrington);' and the same year an American alder, 

 Alnus-'rugosa (serrulata) , at Woods' Hall, Mass., suffered seriously from this 

 this pest (Can. Ent, XXVJ 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 beeri 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 tjiis country. In Europe it is recorded as working on Alnus glutinosa 

 and incana ; the former species in its many varieties is now widely planted in 

 America, ■ix\A. incana \% the common native alder along our northern streams. 



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

 nized. 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 " bhsters " 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 larvje. The mines arp 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. 



The life-history and habits of the insect.— As late as October a few of 

 the larvae were making their characteristic mines and brown " blisters " on the 

 leaves of the trees on the Cornell Campus. The winter is passed as larvse 

 tucked away in their little, brown, elliptical, papery cocoons mostly about half 

 an inch below the surface of the soil beneath the infested trees. In May these 

 hibernated larvaj transform, in about a week, through tender, pale yellowish 

 pupae with brownish-black eyes into the shining black adult insects orsawflies. 

 The adults usually begin to emerge by May 15th, and begin laying eggs at 

 once. On June 8th in 1904, I found many of them busy laying eggs in the 



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

 in 1883. (Beobach. Arten der Blattund Holzwespen, 2nd Abth., 261 as Fenusa pumila) in 

 which the life and habits in late summer are briefly described. 



