1917 ENTOMOLOGICAL SOCIETY. 09 



oross-vein lies behiiul the second cubital cross-vein instead of immediately before 

 it, as in the closely allied elm species, K. ulmi Sund. 



The Egg. The small, round, whitish egg is deposited by the female fly beneath 

 the upper epidermis of the leaf through a slit cut with the ovipositor in the upper 

 surface; the egg is easily recognized as a small yellowish SAvelling in the upper leaf 

 surface. 



The Larva, The larva is six or seven millimetres in length, segmented, 

 slender, whitish in color, or greenish from the food particles ingested, the flat head 

 the true legs brownish, and the prolegs rudimentary. 



The Life Histojiy and Habits. The eggs hatch in a few days, and the_ young- 

 larvffi at once begin feeding upon the pulp of the leaf; the epidermis forming 

 the roof of the blotch mine thus produced, turns brown and makes the work of the 

 larva conspicuous. As the mine increases in size it is frequently bounded on each 

 side by the parellel lateral leaf veins, but when many larvae are working in one 

 leaf, and there may be as many as twenty in a large one, the mines coalesce and 

 may entirely loosen the upper leaf surface, as has been done in figure 7, pi. 2. When 

 an infested leaf is held to the light the larva? may be seen distinctly at work 

 within their mines, figure 1, pi. 2. 



When the larvae are full grown they break through the thin, dead, upper skin 

 of the mine, drop to the ground, and spin a thin silken cocoon slightly below the 

 surface; frequently grains of sand and small pebbles adhere firmly to the silk and 

 form a framework or support for the cocoon. 



The pupal period of the summer broods lasts for about two weeks. The first 

 cocoons of the second generation were started this season in our cages on August 

 8th, and the first adults emerged on August 26th. 



The Number of Broods. There has been some doubt apparently as to the 

 number of broods each season. Dr. Fletcher has recorded two broods for Ottawa 

 in 1891, and Professor Slingerland estimated for Ithaca "at least two or three 

 broods, perhaps more." Our notes on this species were commenced this season 

 early in June, at which time the larvae were abundant in the alder leaves in the 

 Arboretum, although none were noticed then on the native alders. The adults 

 from these larva? commenced emerging about the middle of July, and were 

 abundant by July 20th. Full grown larvae were spinning cocoons again abundantly 

 during the latter half of August, and adults were again abroad in large numbers 

 during the last few days of August, and the first week in September. Eggs were 

 laid early in September, and larvte were working in the leaves until the close of the 

 season. The generations of the season overlapped so that medium-sized and large 

 larvae were present much of the summer, but there was a distinct succession of 

 cocoons, adults and eggs, at three times during the season, in late May and early 

 June, in late July, and in the first week of September. There were three 

 generations of larvae in Ottawa this season, the last spinning the over-wintering 

 cocoons. 



Eemedial Measures. The larvre may be killed within their mines very easily 

 with strong contact insecticides, if the application is made while the larvae are small. 

 Kerosene emulsion and Black Leaf 40 were tested in various strengths. Kerosene 

 emulsion at one part stock to five parts water was fairly effective when applied to 

 foliage containing larvre of all sizes, with 9-t per cent, killed: but was ineffective 

 at one to seven, with only 68 per cent, killed. Probably kerosene emulsion at the 

 strength of one to five would prove satisfactory in the early season while the larvro 

 were all small. 



