44 MASS. EXPERIMENT STATION BULLETIN 189. 



within which it molts to the third instar. This molting cocoon may be 

 located within a single, hoUowed-out flower bud, or may be situated be- 

 neath the webbed-up frass from several flower buds. 



The third instar larva feeds at first within the staminate buds of the 

 tassel in a similar manner to that described for the second instar larva, 

 but, when a little older, it may enter the terminal spike of the tassel, 

 1 or 2 inches above the last branch, and tunnel within this spike, and a 

 small mass of frass collects at the point of entrance and renders the injury 

 conspicuous. Instead of entering the tassel, many third instar larvae 

 tunnel within the midrib of the leaf blade. These tunnels are never 

 more than 1 or 2 inches in length, and closely resemble the injury to the 

 tassel spike. Whether the third instar larva tunnels in the terminal 

 spike, in the midrib of the leaf, or continues feeding in the ends, appears 

 to be arbitrary with the individual. 



The third instar larva may molt to the fourth instar, either within its 

 tunnel or in some protected place outside. If molting occurs within its 

 tunnel, a molting cocoon is not formed, but a silken partition is spim 

 across the entrance hole. If molting occurs in some protected place out- 

 side the tunnel, a typical molting cocoon is formed, and the larva molts 

 to the fourth instar in a similar manner to that described for the preceding 

 ones. 



After molting to the fourth instar the larva usually enters the main 

 stalk of the tassel 1 or 2 inches from its base. Sometimes it enters the 

 terminal internode at the point where the first leaf blade joins its sheath. 

 Later the terminal internode of the corn plant grows so that this en- 

 trance point, instead of being present at the junction of the leaf blade 

 and the leaf sheath, is found 5 or 6 inches above that point. After cut- 

 ting an entrance hole in the side of the stalk the larva tunnels out a small, 

 spherical cell, which occupies nearly all the interior of the stalk at this 

 point. From this it usually tunnels upward for 2 or 3 inches above the 

 entrance hole, and then returns and tunnels downward. During this 

 feeding a large amount of frass is pushed out of the entrance hole and is 

 held there by means of small silken strands spun by the larva. This 

 large mass of yellow-white frass is very conspicuous, and serves to identify 

 infested tassels, even before they break over. Eventually the tassel 

 becomes broken over at the point where the fourth instar larva entered 

 the terminal internode. 



The fourth instar larva molts to the fifth instar within its tunnel, and 

 only spins a silken partition across its entrance, thus using its tunnel for 

 a molting cocoon. 



The fifth instar larva may complete its larval development within the 

 terminal internode. The number of larval instars varies with different 

 individuals, five being sufficient to complete the larval growth in some 

 individuals, while six, or even seven or eight, instars are passed through 

 in other cases. In the majority of instances, especially when an abundant 

 supply of food is available, the fifth instar is the last and longest of the 



