92 REPORT UPON COTTON INSECTS. 



looping would result as before, and in a very short time, often not more 

 than one or two minutes, it would succumb. The number of worms de- 

 stroyed in this way is immense. I am certain that in the field in which 

 I made these observations there were to each square foot of laud at 

 least an average of five dead worms that had been killed in the way de- 

 scribed within a few hours. Other causes tend to render this destruc- 

 tion more complete. Thousands of larvae are destroyed by ants. Many 

 pupae and larvae which have "webbed up" and partially transformed 

 are deprived of their covering of leaves by their voracious companions 

 and fall to the ground where they perish. And still others, apparently 

 more fortunate in transforming within the folds of the leaves of other 

 plants than cotton, are imprisoned in their retreats by their companions 

 which follow and attempt to use the same leaves for the same purpose. 



DISAPPEARANCE OF THE LAST BEOOD. 



Evidently after the disappearance of the brood of worms known as 

 the third crop, one or more broods are usually developed in some parts 

 of the cotton belt. Wherever the earliest spring brood is of consider- 

 able size, there will be developed in the second generation a sufficient 

 number of worms to attract general attention. In this case the fourth 

 brood will constitute the third crop, and there will remain sufficient 

 time for the development of one or two later broods. As already ex- 

 plained these broods are small and attract little attention. Neverthe- 

 less, the disappearance of the last brood is one of the most important 

 points in the life-history of the cotton-worm. It is here that we may 

 hope to learn much on the long-disputed point as to whether the species 

 dies out each year in the United States or not. I regret that I have 

 not been able to make personal observations on this point, as my stay 

 in the field extended only to the first of October. Fortunately careful 

 notes bearing on this subject were taken by Prof. E. A. Smith, at Tus- 

 caloosa, Ala., and by Prof. I. E. Willet, at Macou, Ga. The following 

 quotations from letters which Professor Smith addressed to this depart 

 ment at the time will furnish important details respecting Hie disap- 

 pearance of the autumn brood in Alabama : 



OCTOBER 10. 



The worms have eaten most of the leaves and young buds of the plauts in my Held 

 and are on the move. They may be seen moving through the grass, potato vines, 

 -&c., and upon the trunks of pine trees, seldom, however, higher than live or six feet 

 from the ground, as they jump oft' or fall back after climbing to that height. I do 

 not see that they have begun to eat anything else than the cotton. Most of the worms 

 of the past week or ten days have webbed tip in the cotton leaves, and many chrysa- 

 lides hang from the denuded leaf stalks. They are scarcely at all covered ; the leaf 

 "blade in which they were once wrapped having been eaten away, and they hang 

 almost free in the air. The present brood of worms I find webbing up in the leaves 

 of various plants; the following I have noticed: sweet potatoes, Casein obttix't folia, 

 and C. occidentals, Phijsalis lanceoJata, Solatium Carolinense, sassafras, rimrbilix nil, 

 Ipomea tamnifolia, Sida spinoxa, Ambrosia ar terms iasfolia, Xanthium strumarium, Euphor- 

 bia maculata, Amaruntim Hpinoxnv, (jitercuaaquatica (small tree), sweet gum, watermelon, 



