THE EUROPEAN CORN BORER AND ITS CONTROL. 49 



PUPATION. 

 Location of Pupa. 



Normally the pupa of the European corn borer is found inside the 

 tunnel made by the larva, and not far from its last feeding place. A 

 small per cent of the full-grown larvse, however, leave the interior of the 

 plant when attacking corn and pupate in some protected place near by, 

 such as the silk of the ear; between the husks of the ear; in a fold of the 

 leaf blades; between two overlapping leaf blades; in the frass clinging 

 to the tassel; in the frass at junction of leaf blade and leaf sheath; be- 

 tween the leaf sheath and stalk; and on the surface of the ear in the hol- 

 low made by the feeding larvse. 



Though in corn most of the larvse pupate within their tunnels in the 

 stalk or in the pedicel of the ear, many pupse are found inside the cob 

 and in the upper part of the taproot. 



Cocoon Formation. 



Most of the following remarks concerning cocoon formation apply only 

 when the larva forms its cocoon and pupates within the larval tunnel. 



When the larva reaches full growth and is ready for pupation it cuts 

 a circular exit hole to the surface of the plant. It then spins a silken 

 partition across this exit hole from within, and this partition serves to 

 block the outside entrance to its pupal chamber. It then retreats about 

 2 inches into its tunnel, and forms the base of its pupal chamber by 

 packing the tunnel with a layer of frass about an inch thick. A silken 

 partition is then spun on top of this protecting layer, and frequently 

 another transverse partition of silk is spun about a quarter of an inch 

 above this lower one. After thus closing both ends of the tunnel 

 the larva proceeds to coat the walls of its pupal chamber with a very thin 

 layer of silk, and then spins a single internal partition, also of silk, across 

 the upper part of the pupal chamber and parallel to the exit hole. The 

 larva then constructs two slanting partitions in the lower part of its pupal 

 chamber, which intersect each other and form a partition resembling the 

 letter "Y." 



After completing the bottom partitions of the pupal chamber the larva 

 turns around and begins forming the upper ones. These are quite similar 

 to the lower, but are usually more complicated and more substantial. 

 They consist of a series of four or five intersecting partitions of silk which 

 meet in the center to form a letter "Y", and make an angular roof over 

 the head of the larva. The cocoon is then complete. About three or four 

 days are usually required by the larva for its formation. 



After completing the upper partitions of its pupal chamber the larva 

 attaches its anal legs firmly to the angle of the "Y" in the bottom par- 

 tition, and then passes into a semi-quiescent state. 



