83 



PUPATION IN OTHER SITUATIONS. 



While it is the normal habit of the bollworm to burrow beneath the 

 soil to pupate, it will rareh^ either from necessity or otherwise, choose 

 other situations. Coquillett (Ins. Life, I, p. 331) records four pupae 

 of the late fall brood which were found by him in ears of corn at Los 

 Angeles, Cal. Probably the warm winter climate of that region may 

 be a factor in developing such an unusual habit. In several instances 

 larvae confined in the laboratory with corn ears as food, but without 

 earth, have pupated in a cavity eaten out of the ear. When this is 

 done usuall}^ small bits of the surrounding tissues, or of paper, if 

 such is present, are webbed together to form a sort of cocoon which 

 more or less successfully conceals the pupa. In all our experience, 

 however, not one was observed which had pupated in a cotton boll. 

 This is probably on account of the rapid decomposition undergone by 

 the injured bolls. In practice we obtained great numbers of pupae by 

 confining large larvae under inverted tumblers supplied with sufiicient 

 food, but without soil. 



CHANGES UNDERGONE IN THE FORMATION OF THE PUPA. 



At the time it enters the soil the larva is somewhat stouter than it 

 was just before, and the incisions between the body segments are 

 beginning to become more distinct. (See PL XII, fig. 2.) When it 

 has formed its cell a period of quiescence ensues, which usually lasts 

 for from two to four days for the summer broods and much longer 

 for the fall brood. During this time the larva decreases in length, 

 gradually approximating the length of the pupa, and at the same time 

 becoming stouter in the middle and more tapering distall}^, the inter- 

 segmental constrictions growing more apparent. (PI. XII, fig. 3.) 

 The coloring generally becomes less brilliant and tends toward a 

 greenish or yellowish tint with black markings. 



The larval skin splits medially along the dorsum of the thorax and 

 the head of the pupa is passed through the opening, after which the 

 skin is rapidly worked backward by the movements of the body, 

 finall}^ forming a loose mass at the base of the cremaster, where it is 

 easily thrown ofi' entirely. This operation is all accomplished in the 

 brief space of four or five minutes. The pupa is now very pale in 

 color, usually with the head and thorax lemon-yellow, or often dis- 

 tinctly greenish, especially on the thoracic dorsum and appendages, 

 with the spiracles brown and the abdomen cream}^ yellow. After an 

 hour or two the abdomen has darkened considerably, the integument 

 assuming a brown color and concealing the fat bodies beneath. From 

 twelve to eighteen hours are required for it to gain the uniform 

 brownish tint, which continues to darken for several days longer. 

 Pup^ forming late in the fall do not undergo this final darkening until 

 a short time before emergence the next spring. 



