to the production of an immense number of weevils very late in the season and at just the right time for their successful hibernation. As the result of this, far greater injury is done to the crop of the following season, with a comparatively small gain in the yield of the present season. Furthermore, plants standing until frosts kill them are often allowed to stand throughout the remainder of the winter, and these furnish an abundance of favorable hibernating places for the weevils. The consequence of this practice is that so many weevils are carried through the winter alive that the yield of the next year will be much less than what it might have been but for the farmer's indulgence of the forlorn hope of a top crop.

From these considerations it seems plain that within the weevil territory all hope of a top crop must be given up and the destruction of the stalks be practiced as early in the fall as may be possible. This practice is one of the essential elements in the successful control of the weevil.

SOME REASONS FOR EARLY DESTRUCTION OF STALKS.

It is naturally impossible to fix any date for the destruction of stalks which would apply to all localities and under all conditions. The condition of the soil must be considered as well as that of the maturity of the crop. While the condition of the soil can not be changed, the time of the maturity of the crop is largely within the control of the planter, since by early planting of early maturing varieties nearly the entire yield may be matured before the usual time of picking of the first cotton from native seed. Whatever the qualifications which must be made, they do not decrease the general strength of the reasons which may be given for the early destruction of stalks. The principal reasons are three in number:

First, the absolute prevention of development of a multitude of weevils which would become adult within a few weeks of hibernation time. The destruction of the immature stages of weevils already present in infested squares is surely accomplished, while the further growth of squares which may become later infested is also prevented. This stops immediately the development of weevils which would normally hibernate successfully, and by decreasing the number of weevils which will emerge in the spring the chances of a good crop for the following season are greatly increased.

The second reason is that by a proper manipulation of the stalks a very great majority of the weevils which are already adult can be destroyed. One of the most successful practices is to throw the stalks in windrows, and as soon as they have become sufficiently dry they may be burned. If the weather is favorable, the burning may take place in about two weeks, and many of the weevils will not have left the cotton stalks by that time. In case rains delay the drying it will be found advantageous to expedite burning by the use of crude petro

leum. Grazing the fields with cattle, as some have recommended, will destroy much of the growth and prevent further development of weevils, but it allows enough of foliage to remain to sustain the life of many which are already adult until it becomes sufficiently cold for them to hibernate. Not only does burning destroy most of the weevils, but it also destroys the shelter which might be afforded the few that would escape, and the chances of successful hibernation are largely decreased by this practice.

The third reason may be found in the fact that the clearing of the ground renders possible a deep fall plowing. This catches such weevils as might still be in squares on the ground. The ground becomes clean by this practice, so that no vestige of the food plant remains, and living weevils, if by any possibility they have escaped thus far, must either starve or perish from exposure. Furthermore, fall plowing places the ground in the best possible condition and makes it ready for immediate working as early as planting may begin in the spring, thereby saving delay in the starting of the crop. As stalks must be destroyed in some way before the field can be replanted, the practices here mentioned will not add greatly to the cost of destruction. Even if some cotton is present upon the stalks at the time of their destruction, this small item is hardly worthy of consideration in comparison with the greatly increased crop and the more early maturing and better quality of staple which may be obtained by the adoption of this recommendation.

Having studied carefully the methods of weevil control which have heretofore been recommended, the writers firmly believe that the destruction of the stalks in the early fall is the most effective method known of actually reducing the numbers of the weevil. Early destruction will cost but a small fraction of the expense necessary to the frequent picking up of the squares infested by hibernated weevils in the spring, and is far more thorough as a means of reducing the numbers of the weevil than is the practice of picking hibernated weevils from the young plants.

Early destruction of the stalks is essential to the greatest success of any system of controlling this pest. All other practices recommended-early planting of early maturing varieties, thorough cultivation, fertilization, etc. (see p. 112)-though very valuable in securing the crop, are perhaps of greatest value because they prepare the way for this early destruction which so reduces the actual number of weevils hibernating successfully that the other recommendations may yield their best results. Since the earliest investigations made by this Division upon the boll weevil, it has been recognized that this practice is of the first importance, and the experience of recent years has but added certainty to this conviction. Planters have, however, been slow to change their methods of cultivation, but enough have adopted the recommendation to prove its efficiency. It must not be thought

that the procuring of the immediate crop is the only desideratum. Early and complete destruction of stalks is undoubtedly the most important single element insuring success for the subsequent year.

DISSEMINATION.

Two principal periods of dissemination may be found during a season. The first is when the hibernated weevils leave their winter quarters and go in search of food. Having found food, the spread is mainly controlled by the limitation of the food supply. So long as an abundance of growing tips or of clean squares is near at hand weevils will not travel far, but when the condition of total infestation is reached the period of greatest dissemination is also attained.

In any given field dissemination takes place mainly by the short flights and crawling of the weevils. The search of the female for uninfested squares is the principal factor in their movement. Heavy winds seem to be of comparatively small importance, as weevils do not take flight readily at such times; but light, warm breezes, such as prevail throughout the coast country of Texas, undoubtedly tend to carry them in a general northerly direction, and the continuous equinoctial storms of the fall in Texas, occurring at the very time the pests are most active, have undoubtedly had a strong effect in the same direction.

The two principal lines of spread will be found along railways and water courses. Between localities separated by short distances, traffic along highways is probably the chief factor. The distance which a weevil may travel in flight has never been determined, but from a study of their habits of flight it would seem to be comparatively short. Floods and the motion of water along water courses frequently serve to distribute many weevils along the edge of high-water mark. As river valleys are largely devoted to cotton culture, this would seem to be no small factor in the transportation of the weevils.

Over longer distances the usual means of commercial traffic must be held responsible. Shipments of cotton, whether for ginning or in baled condition, are likely to carry many weevils. Shipments of seed for planting, coming from infested localities, are almost certain to carry weevils, and shipments of seed to oil mills may also assist in scattering them. The pests are often carried far outside of infested regions in the shipment of seed to northern oil mills. From the mills. they are carried to the farms in the hulls or other by-products used for feeding cattle. Many of the isolated colonies in northern Texas originated in this manner.

WEEVILS IN SEED HOUSES AT GINNERIES.

Careful observations made by Mr. Schwarz at Victoria throughout the winter of 1901-2 revealed great numbers of weevils about the gins. They occurred especially in the seed houses, and the danger of the

transportation of the pests from one locality to another was most evident.

A casual examination of the dirt separators which are now in use in the more modern ginneries shows that immense numbers of weevils brought in from the fields are separated from the lint by these devices. Even where these separators are used, however, a short search in the seed house will show that many weevils pass through alive. A single hour's search in the seed house of a first-class ginnery, where dirt separators are in use, yielded seven boll weevils in perfect condition, and a number of other and much larger insects. In addition to these a number of fairly large spiders, most of which were in perfect condition, were also found. Numerous pupa may pass through the gins unharmed in the cells formed by the larvæ. These cells are similar, both in size and shape, to the seed, and may often be mistaken therefor (Pl. XI., fig. 44). Distribution of weevils in seed is therefore easily possible, and uninfested localities should guard carefully against importing weevils in this way.

The most valuable suggestion for reducing the important effect that gins have in spreading the weevil is in the improvement of the cleaning devices referred to above, and in encouraging their more general use. A particular study of this matter will be made during the season of 1904.

NATURAL CONTROL.

Doubtless many factors are concerned in the natural control of the boll weevil. The most important ones are probably included among the following topics:

MECHANICAL CONTROL.

PILOSE OBSTACLES TO WEEVIL PROGRESS.

In testing the susceptibility of various cottons to weevil injury it was found that the variety of Egyptian cotton grown (Mit Afifi) was more severely injured than was any other. The next in order were Sea Island and Cuban tree cotton, while the American cottons, represented especially by King's Improved, were less severely injured than were any of the others. It may be noted that the three varieties first mentioned seem more closely related to each other than any of them do to the American. The reason for the evident choice of these cottons was carefully sought for, but the only difference which seemed worthy of consideration was found in the varying degree of pilosity upon the stems (Pl. XIII, fig. 50). It was found that Egyptian stems were almost perfectly smooth, while Sea Island and Cuban resembled it closely in that respect. Many American cottons, and King's Improved especially, are quite pilose, and it was often noted that upon these weevils showed some slight difficulty in moving about or in climbing the pilose stems of the plant. While this obstacle to weevil

activity may seem slight to account for the evident selection of the smoother varieties, no greater difference could be found. As is shown by Table XI, on page 46, the selection is not due to a difference in taste of the squares.

In order to test the resistance which varying degrees of pilosity might offer to weevil progress, a number of experiments were made with various stems or fruits. In climbing upon the stems of King plants weevils would catch the spines with the forefeet while pushing themselves upward by means of the tibial spurs of the hind legs placed against the epidermis and between the spines. It was evident that their progress was considerably hindered, and several attempts were often made before a firm foothold was secured.

Okra pods were next tried, as upon them the spines are very short and stiff. Weevils climbed these pods with little difficulty.

The seed pods of Sunset Hibiscus were also tested. The spines upon these are from 2 to 3 millimeters long; they stand thickly and are quite stiff. Over these spines weevils walked easily, but though they attempted vigorously to get their heads down between the spines far enough to feed, they were unable to do so. A number of weevils were kept for several days upon these pods, but they were unable to feed. The spines were then removed from a small area, and the insects began to feed immediately.

Weevils travel with difficulty over loose cotton fibers, as their feet become entangled among them.

DESTRUCTION OF LARVÆ AND PUPE IN BOLLS AND SQUARES BY ABNORMAL PLANT GROWTH.

In making examination of several thousands of infested squares a small percentage was found in which the larvæ had evidently been killed by an abnormal condition of the interior, which may be characterized as a process of gelatinization. This change begins at the point of injury and spreads. Instead of the normal growth of the anthers there takes place a change which appears to be something like the swelling of starch granules. The interior becomes soft and pulpy, and by the swelling considerable internal pressure is produced. The death of the larvæ results either from unfavorable food conditions or from the internal pressure, which in many cases is sufficient to distort the square. Whether from these or other causes, from 10 to 20 per cent of the larvæ usually die within the squares.

Gelatinization sometimes occurs in small bolls, but more rarely as bolls become larger and more mature. In large bolls in which seeds are nearly matured the feeding of the weevil larvæ often causes seeds to sprout, and in several such cases pupæ have been found crushed by the rapid growth of the caulicle.

In examining nearly 1,000 bolls, taken partly from King and partly from native cotton, it was found that in the early maturing King the