314 REPORT UPON COTTON INSECTS. 



tion the fact that rotation of crops has been strongly urged as a preventive 

 against the ravages of the boll- worm. The knowledge which we have 

 gained of the multivorous habits of the insect readily shows us that 

 such a course would be vain, as during the season when cotton was not 

 grown some other food-plant would be available. As a curiosity we may 

 mention the fact that some years ago a writer in the Southern Cultiva- 

 tor, after earnestly urging rotation of crops, advises corn as the best crop 

 to rotate with cotton ! 



DESTRUCTION OF THE CHRYSALIDES. In the more southern portions 

 of the cotton belt, where the frosts are rarely severe, but little can be 

 done toward the destruction of the chrysalides beyond instructing the 

 plow-hands to crush them whenever they observe them in plowing, or 

 causing a boy to follow the plow and collect them as they are brought 

 to the surface. In the more northern portions, however, fall plowing 

 may accomplish much good. Experiments, having the testing of the 

 efficacy of this remedy in view, have been made by Professor French. 

 We can do no better than to give his own words : 



Fall plowing. To make it plain how this is to reach them, I shall have to explain 

 some observations made on the fall brood of chrysalides that were found during the 

 month of November in a field where the worms had been very abundant in the corn 

 before it was harvested. In digging for the chrysalides round the corn-hills, I found 

 that instead of their occupying an oval earthen cocoon, as has usually been written 

 of them, and as they apparently do in the breeding-box, they were down in the ground 

 from five to six inches below the surface, in a hole about a third of an inch in diameter, 

 reaching from the chrysalis to the top of the ground, where it was covered over with 

 a thin film of dirt from an eighth to a quarter of an inch thick. This hole was larger 

 at the bottom than at the top, apparently so as to give free motion to the chrysalis, 

 and usually bent in its course, so that the lower part would have an inclination of 

 perhaps forty-five degrees. At the bottom would be found the chrysalis, the small 

 end downward and the head upward. 



In one case I found the hole so bent that the chrysalis occupied a horizontal position. 

 The hole was smooth inside, and was perhaps made so by cementing the dirt together; 

 but of that I could not tell, for the whole ground was moist, though dry enough to be 

 firm. I took several of the chrysalides and put them in a box with some loose dirt, 

 and then moistened it, after which I allowed them to freeze. The dirt, when they 

 were allowed to freeze, was dry enough, so that if it had been in the garden and 

 . turned over with a spade it would crumble. When examined, after the freezing, all 

 were dead. Some others taken up in the bottom of their subterranean habitations, 

 without sifting the loose earth round them in their holes, and allowed to freeze, were 

 not killed by freezing. 



My conclusions were, that so long as they were in the smooth compartments they 

 had made for themselves, free from any loose dirt that would became wet and stick to 

 them, they could pass the winter in safety, even though they might bo frozen ; but, 

 when the dirt was packed loosely round them and became wet and stuck to them, then 

 freezing killed them. Their holes, running cell-like as they do from the surface down 

 into the ground five or six inches, must be broken up by plowing, and when once 

 broken up with the loose dirt round them the rains and the freezing winter weather 

 would have the same effect on the chrysalides that moisture and freezing had on those 

 in the box of loose dirt. Fall plowing, then, for these reasons, will probably be the 

 most efficient means of destroying these insects ; besides, if done late enough, it will 

 rid the ground of cut- worms, &c. 



