THE SEMITROPICAL ARMY WORM. 67 



on the vines and onh' a few live ones, but the same conditions were 

 observed on the check rows. The experiment was an absohite failure. 



Experiment No. 11. — July 29, plants were sprayed with copper 

 arsenite mixture at the rate of 15 ounces to 50 gallons of water. In 

 this case 1\ ounces of copper arsenite and 1 quart of thick lime were 

 used with 5 gallons of water. Two days later the spray showed better 

 than in experiment No. 10 because of an abundance of lime and was 

 very fineh' and evenly applied to the leaves. Four larvae were dead 

 on a few plants examined against 32 living Prodenia and 3 living 

 sweet-potato sphinx-moth larva^ {Phlegethontius ronrohmll L.). 



August G, this spray still remained on the foliage, seeming to 

 adhere well, but the experiment was a failure in killing larvtr. 



Exjjeriment No. 12. — July 20, plants were sprayed with arsenate of 

 lead, 3 pounds to 50 gallons of Avater, applied as in previous experi- 

 ments with lead arsenate. There was no rain for 24 hours. On a few 

 plants examined three days later 41 dead larva^ were found and 40 

 living, an observed death rate of less than 50 per cent. It should be 

 pointed out at this time, however, that it is difficult to find dead larvae, 

 as they sometimes dr}^ up or craAvl away. 



August 2, the vines were almost free from larvae. The experiment 

 was jDronounced very successful. 



Experhnent No. 13. — July 30. arsenate of lead, 2 pounds to 50 gal- 

 lons of water, was used without ensuing rain. In some rows exam- 

 ined August 1 about 20 per cent of the larva* Avere dead ; in others 48 

 per cent, 54 per cent, and Gl per cent were killed in two days. August 

 5, these rows appeared entirely free from larva' unless closely in- 

 spected, when only 5 or G could be found to a row. These might have 

 craAvled from unsprayed Aveeds or other plants. 



Experiment No. lJf.—^w\\ 30, arsenate of lead, 3 pounds to 50 gal- 

 lons of Avater, was used. Three daj^s later 84 per cent of the larva? 

 under observation Avere destroyed, the rows being quite clean. In 

 both of these experiments, 13 and 14, manj^ dead larva* Avere found in 

 rows not sprayed, as many as five rows away from the sprayed ones. 



Expenment No. 15. — August T, arsenate of lead, 2 })ounds to 50 

 gallons of Avater, Avas sprayed b}' a laborer, under supervision. It 

 rained at 1 p. m., but the spray remained on the leaA'^es in large 

 amounts and, for having been applied by an inexperienced hand, was 

 well distributed. In this experiment, for some reason, the first four 

 rows sprayed at one filling of the tank produced quite a number of 

 burned leaves. This Avas attril)uted to a possible mistake in Aveigh- 

 ing out the chemicals. It did not, hoAveA'er, permanently injure the 

 plants. 



Caterpillars in the last 4 experiments, supposedly of the third gen- 

 eration, were A'ery small, not over one-foiirth or one-third of an inch 

 in length. As a consequence they were quickly killed, large numbers 



