370 REPORT 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 



tacked and ate into ayoun^ boll, and liad increased to thirteen-twentietlis of an inch 

 in length. From this time it ate nothing but the inside of the boll, and on the twentieth 

 day the skin was again shed and it had grown to the length of an inch and one-tenth, 

 but, unfortunately, died before completing its final change. 



There is, however, in this instance something of an abnormal character 

 in addition to the fact that the measurements of the early stages are ob- 

 viously insufficient. The growth was evidently watched in a breeding- 

 cage, and perhaps at the North. 



The full-grown, well-developed worm averages 4«™ (1. 57 inches) in 

 length and about 7"^"* (0. 27 inch) in diameter. On arriving at full 

 growth the worm works its way to the ground, and, choosing a spot 

 where the earth is somewhat compact rather than loose and friable, bur- 

 rows beneath the surface and forms a subcylindrical, straight or sloping 

 galldry to the depth of from three to six inches. This gallery is slightly 

 closed at its mouth and gradually widens towards its lower end, where the 

 worm transforms to pupa. 



The pupa (Plate III, Fig. 6). —The old and generally accepted state- 

 ment was that the pupa of Heliothis is found underground in an oval 

 cell composed of particles of earth held together by a loose, gummy silk. 

 In Illinois, at least. Professor French has found that the winter brood 

 pupates in a somewhat different way. We quote from his article in the 

 Frairie Farmer of October 2Q, 1878 : 



When the larva attains its growth it descends to i^he ground, into which it goes to 

 pupate. In doing this it usually selects some place where the earth is rather firm, 

 seeming to prefer the security a compact soil can give, to ease in digging. 



It digs a hole into this several inches in depth apparently cementing the dirt as it 

 goes down, so that when it reaches the desired depth there is a smooth channel from 

 the bottom to near the surface, there being a thin film of dirt over the entrance. 



This hole, as I found in digging about corn-hills, is about a third of an inch in 

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

 the chrysalis, and is usually bent in its course so that the lower part would have an 

 inclination of often as much as forty-five degrees. I found the chrysalis at the bottom 

 of this, the small end downward. In one instance I found a hole so bent that the 

 chrysalis occupied a horizontal position. * * » i began digging for the chrysalids 

 in November in a field where the worms had been abundant in the corn, using at first 

 a spade and digging at random. I had expected to find them in oval " cocoons," as 

 they were supposed to make, but cutting across channels in which I afterwards found 

 chrysalids led me to dig a little more carefully. I soon found that by running the 

 spade along the row and and taking off half an inch or less of the surface I could tell 

 where every chrysalis was to be found. 



The presence or absence of this smooth coherent tube or '' channel," 

 as Professor French calls it, depends greatly, without doubt, upon the 

 friability of the earth in which the burrow is made, as extremely loose 

 earth would fall in upon the worm, obliterating the tube. The "oval 

 cell" is nothing ^lore nor less than the rounded ending of the tube, and 

 it would be a stretch of the imagination to call it an earthen cocoon, yet 

 a thin fihn of silk is usually to be seen upon the walls. 



Deprived of all earth, we have known the Boll Worm to pupate 

 nakedly and in apparently as healthy condition as though the surround- 



