In from one to two weeks the grub or larva becomes fully grown and, without changing its home, is transformed into the pupa state. Then in about a week more the pupæ come out as adult weevils and attack the bolls. They puncture them with their snouts and lay their eggs in the bolls. The young grubs, this time hatching out in the boll, remain there until grown, when they emerge through holes that they make. These holes allow dampness to enter and destroy the bolls. This life-round continues until cold weather drives the insects to their winter quarters. By that time they have increased so rapidly that there is often one for every boll in the field.
This weevil is proving very hard to destroy. At present there seem but few ways to fight it. One is to grow cotton that will mature too early for the weevils to do it much harm. A second is to kill as many weevils as possible by burning the homes that shelter them in winter.
Fig. 178. A Cotton Boll with Feeding-Holes of Weevil, and Bearing Three Specimens of the Insect | Fig. 179. The Mexican Cotton-Boll Weevil, showing Structure |
The places best adapted for a winter home for the weevil are trash piles, rubbish, driftwood, rotten wood, weeds, moss on trees, etc. A further help, therefore, in destroying the weevil is to cut down and burn all cotton-stalks as soon as the cotton is harvested.
This destroys countless numbers of larvæ and pupæ in the bolls and greatly reduces the number of weevils. In addition, all cornstalks, all trash, all large clumps of grass in neighboring fields, should be burned, so as to destroy these winter homes of the weevil. Also avoid planting cotton near trees. The bark, moss, and fallen leaves of the tree furnish a winter shelter for the weevils.
Fig. 180. A Series of Full Grown Weevils,
showing Variations in Size
A third help in destroying the weevil is to rotate crops. If cotton does not follow cotton, the weevil has nothing on which to feed the second year.