122 THE GYPSY MOTH. 



have been benefited by such burning, as they have shown a 

 better growth during the season following. Oil is poured 

 in at the top of the hollow, and a sufficient aperture made 

 at the bottom to ensure a good draft. The oil is then 

 lighted, and the draft in the funnel thus made fans the 

 flame until the decayed wood has been consumed. This 

 should be done only in the winter, when the sap is dor- 

 mant, and the fire should be extinguished before it has done 

 serious injury to the live wood. This treatment is unnec- 

 essary in cavities so accessible that the eggs and dead wood 

 may be removed by other means. 



The naphtha burner, an instrument commonly used by 

 painters and plumbers, was used in 1891 as a substitute for 

 the scraping of eggs from trees and rocks, which sometimes 

 resulted in their being scattered. This burner is supplied 

 with an air pump, and furnishes an air-blast flame of an ex- 

 tremely fierce heat. If this flame is applied directly to the 

 egg-cluster, it will reduce it to ashes on the tree, although 

 occasionally eggs exposed to such great heat will burst, 

 possibly scattering others. The burner should be used only 

 on the trunks of large trees having thick bark, or in such 

 cavities in trees or rocks as cannot be reached by other 

 methods. 



Killing the Eggs with Chemicals. 



Early in the work of 1891 it was seen to be impossible to 

 detach the egg-masses from their various places of deposit 

 without occasionally scattering and losing some of the eggs. 

 Experiments made during the following winter proved that 

 eggs scattered and exposed to the vicissitudes of the season 

 were not all destroyed by frost or snow, but that about two- 

 thirds of them hatched in the spring. It was seen that it 

 would be wiser and safer to destroy the eggs without re- 

 moval, and experiments were made with that end in view. 

 The most successful method at first used was the application 

 of acids which in combination destroyed the eggs. The 

 apparatus was designed and the method invented by Mr. 

 F. C. Moulton, a chemist employed in the gypsy-moth work. 

 The apparatus (Fig. 2) was composed of a small tin case hold- 

 ing two bottles, each of them having a rubber stopper with 

 two glass tubes, each of which projected into the bottle as 



