338 REPORT OF THE COMMISSIONER OF AGRICULTURE. 



lepidopterous larvae, of devouring one anotlier. All through the past 

 summer larvae were being sent to the department from the South, but 

 whenever several boll- worms were mailed in the same box, one only 

 would reach us alive, all the others having been destroyed. This was 

 the case even when the box was filled with cotton leaves and bolls or 

 corn leaves. It might, however, be said that the food dried up on the 

 journey, and that hence they were driven to destroy one another; but 

 the fact is that even when confined in breeding cages, where fresh food 

 was always at hand and where the conditions were mad-e as natural as 

 possible, they seemed as hungry as ever for their companions, and it 

 was impossible to rear more than one in the same box or cage. 



Still more conclusive, however, and of extreme interest, is tlie fact 

 that Mr. Trelease actually saw, upon several occasions, on the plant 

 and undisturbed, large boll-worms catch smaller ones, which they de- 

 voured " hoof and hide," or simply pierced the skin with their mandi- 

 bles so that the juice could be sucked, the refuse being dropped. 



In addition to this we have the fact fully established during the past 

 season that the boll- worm, in a state of nature, preys more or less fre- 

 quently upon the chrysalis of the cotton-worm. 



In the specimens sent to the department, the full-grown boll-worm 

 was found entirely within the folded leaf and the hind end of the body 

 of the chrysalis was eaten into. 



Judging from the data at hand, the duration of the larva state of 

 Eeliothis, or, in other vjords, the worm state, seems to vary fi'om eighteen 

 to twenty-four days in the cotton-beit, depending much upon the climate, 

 the state of the weather, and the food plant. When full-grown it trans- 

 forms to a chrysalis, with very different preliminaries from* those which 

 prepare the cotton-worm for pupation. 



THE CHRYSALIS. 



Almost all of the statements regarding the pupation of the boll- worm 

 have been to the effect that the full-grown worm descends into the 

 ground to the depth of several inches, and there forms itself an oval 

 cocoon of gravel and earth, cemented together by its gummy sdk. 



Prof. G. H. French, of Illinois, has studied the chrysalis of MeliotMs 

 carefully of late, and sums up his observations as foUows : * 



la digging for tlie chrysalis around the corn-hills, I found that instead of their oc- 

 cupyii7g 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 aliout a third of an inch in diameter, reaching from 

 the chrysalis to the top of the ground, where it was covered 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 full motion to the chrysalis, and usually bent in 

 its course, so tlie lower part would have an inclination of perhaps forty-five degrees. 

 At the bottom would be found the chrysalis, the ^mall end downward and the head 

 u^jward. In ouc case I found the hole so bent that tho chrysalis occupied a horizontal 

 position. The hole was smooth inside, and was, jjerhaps, made so by cementing the 

 earth together, but of that I could not tell, for the whole ground was moist, though 

 dry enough to be firm. 



In reference to these observations of Professor French, Mr. Trelease 

 says, in a recent letter : 



In der-p breeding-jars, with four or»five inches of loose soil, I found that the larvae 

 of Hetiolhis went several inches from the surface before forming their cocoon, but did 

 not notice a passage leading down. As I did not notice very closely, such a tube may- 

 have been there, but I think if so I should have seen some trace of it. In all cases 

 there was a thin fihn of silk. In the field I saw numbers plowed up, but did not dig 

 for any with care. Of course the plowing would have destroyed such a tube, but I 

 sometimes found the silk about the pupa, though always more or less torn. 



* Seventh Report of the State Entomologist of niiaois, 1877, p. 105. 



