510 BULLETIN 333 



as though they had taken a new hold on life (Fig. 171). A row of the 

 same kind of trees of about the same age, not far from these, nearly all 

 died during the summer and were cut down (Fig. 170). It is evident 

 that the "Black-leaf" extract does not work so fast as does the 

 "Black-leaf 40." 



Eight other trees were sprayed on May 28 with " Black-leaf 40 " (which 

 contains 40 per cent nicotine), at the rate of i pint to 100 gallons of water, 

 with 5 pounds of fish-oil soap and 3 pounds of powdered arsenate of lead 

 added. These trees, which had been badly injured by the miner in pre- 

 ceding seasons, were in good condition at the end of this season. All the 

 young miners and many of the older ones were killed at once in their 

 mines. Here and there, where the leaves had not been thoroughly coated 

 with the mixture, some of the larvae that were larger and older at the 

 time of spraying escaped. 



One Camperdown elm was sprayed thoroughly. It was low and the 

 leaves could be coated thoroughly on both sides. The miners were com- 

 pletely held in check on this tree. 



On the whole, the work showed that this pest of the European elms 

 can be held in check if taken at the proper time. The trees must be 

 sprayed early, just as soon as the tiny mines begin to show in the leaves. 



The " Black-leaf 40," i pint to 100 gallons of water with 5 pounds 

 of soap, seems to be more effective than the " Black-leaf." One great 

 advantage of these tobacco extracts is that the arsenate of lead may be 

 added for the leaf -beetle, thus obviating the necessity of a separate spray- 

 ing for each insect. 



It might be well to say that " Black-leaf 40 " is a tobacco extract 

 manufactured by the Kentucky Tobacco Product Company, Louisville," 

 Kentucky. It may be bought from that firm direct, or it may be pro- 

 cured from several distributing agents in the State. It is sold by the 

 Leadley Drug Company, Batavia, the Rex Company, Rochester, and the 

 Parsons Drug Company, Albion. The price is $12.50 per gallon or 

 $1.85 per pint. When it is diluted at the rate of i pint to 100 gallons 

 of water, however, it costs no more than lime-sulfur or other contact 

 insecticides. 



LIFE HISTORY OF THE ELM LEAF-MINER 



The adult insect is a small, shining black sawfly about one eighth of 

 an inch in length. The wings expand about one third of an inch. In 

 the latter part of May the sawflies may be seen on the leaves of the elm. 

 They are not shy and can often be picked up with the fingers. 



The tiny, milk-white eggs are thrust by the female into the tissues 

 of the leaf from the upper side. They hatch in about one week and the 



