81 



j 1904, we saw a full-grown larva leaving a cotton plant at 9.30 in the 

 morning. It climbed cautiously" down the stem, once stopping to 

 ! crawl out on a branch near the ground. 



FORMATION OF THE PUPAL CELL. 



Once a larva has reached the ground, it proceeds at once to select a 

 suitable place to burrow beneath the soil. Under ordinary conditions 

 not much time is lost in choosing the proper site, which is usually not 

 more than 1 or 2 feet from the base of the plant. When confined 

 within a small space a few minutes are always sufficient. It now begins 

 to push its head against the soil, at the same time swinging it slightly 

 from side to side, and thus throws up a pile of loosened particles of 

 earth. (See PL XII, fig. 1.) The diameter of the hole when excava- 







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Fig. 8. — Diagram of different types of pupal cells (original). 



tion begins is about twice that of the larva, but soon becomes blocked 

 up by the loose earth. The time required to get beneath the surface 

 varies anywhere between five minutes and three-quarters of an hour 

 or even much longer, depending on the texture of the soil and the 

 activity of the larva. When it has passed from view beneath the sur- 

 face it continues to work down in a more or less slanting direction to 

 a depth of from 1 to T inches, leaving the pile of loose earth to mark 

 the point of its entrance. So far all its actions have been preliminary 

 to forming the pupal cell, which is not constructed along the path by 

 which the larva entered the soil, as had been generally supposed. 



