THE SEMITROPICAL ARMY WORM. 65 



observed feeding on the eggs of the latter.*^ The cabbage worms were 

 between one-quarter and tliree-eighths of an inch in length at this 

 time. 



A FUNGOUS DISEASE. 



Empusa sp. — September 8, 1007, a few Prodenia caterpillars, which 

 Avere found dj'ing of a fungous disease in our I'earing cages, were 

 referred to the Bureau of Plant Industry for identification of the 

 fungus. Mrs. F. W. Patterson stated that it was a species of Empusa. 



METHODS OF CONTROL. 



The arsenical poisons are effective against this army worm under 

 ordinary conditions. Experiments performed at Orlando, Fla.. how- 

 ever, brought out the fact that Paris green, on account of the frequent 

 rains which occur at the height of the principal outbreaks in the 

 infested regions of Florida, such as Orlando, is almost ineffective and 

 it is therefore necessary to use arsenate of lead. Owing to the 

 greater adhesiveness of the latter it remains on the plants when the 

 former is washed off. 



Paris green, arsenate of lead, and a special preparation which may 

 be called adhesive copper arsenite, were tested, the last by request of 

 its inventor. It was used in experiments Xos. 8, 10. and 11. A barrel 

 sprayer, fitted with Vermorel nozzle, was used for a number of these 

 experiments, but for most of them a knapsack sprayer of fine quality 

 was employed. Sweet potatoes were sprayed in ever}^ case except in 

 experiment Xo. 5, where collards were also sprayed, and the work was 

 iisuall}^ begun between 8 and 10 a. m. in bright sunlight. Spraying 

 experiments commenced July 12 and were continued until August 7. 



Expeiinient Xo. 1. — July 12. infested plants were sprayed with 

 a solution of Paris green, 5 ounces, and freshly slaked lime, 5 ounces, 

 in 50 gallons of water. The spraying was done in the morning and 

 rain fell before noon. The next day when the field was examined 

 the larva^ were found uninjured and practically no poison remained 

 on the leaves. The experiment Avas therefore a failure. 



Exferiment No. 2. — July 12, Paris green, 8 ounces, and freshly 

 slaked lime, 1 pound to 50 gallons of water, were sprayed the same 

 day and with the same results. 



Experiment Xo. 3. — July 17, Paris green was sprayed as in Xo. 2. 

 Again rain fell hard and steadily before noon, with the same results 

 as in experiments 1 and 2. 



"This would soeni to furnish at least one reason why this important insect 

 has been al)le to supplant its American cousins such as Pontia napi L., P. pro- 

 iodice Bdv. & Lee, and P. monufite L., all of which feed on crucifers and are 

 called cabbage butterflies or " worms." 



