longitudinal groove in the stalk and within the shelter of the clasping base of the leaf. Perhaps the most favorable of all hibernating conditions are to be found among the leaves and rubbish abounding in the edges of timber adjoining cotton fields. From such places the weevils are known to come in large numbers in the spring. The timber fringes present greater difficulties in the way of removing the favorable conditions than do any of the other places mentioned.

Temperature and available food supply seem to be the most important factors in determining the time of hibernation. In general, it may be said that many weevils are active so long as their food continues in fit condition to sustain them. Some, however, undoubtedly seek shelter before frosts occur. From numerous observations made in the laboratory, it appears that weevils will starve when deprived of cotton if the mean average temperature continues long above a point somewhere between 60° and 65° F. As the mean average falls below 60° hibernation may take place successfully.

It is a very significant fact that of the 240 weevils taken from the field at the middle of December, 1902, and placed in hibernation, 38, or 15 8 per cent, passed the winter successfully, while of the 116 weevils adult before November 15, 1903, only 1, or less than 1 per cent, survived. It is evident that the weevils which pass the winter and attack the crop of the following season are among those developed latest in the fall and which, in consequence of that fact, have not exhausted their vitality by oviposition or any considerable length of active life.

LENGTH OF HIBERNATION PERIOD.

As the observations upon this point håve all been made at Victoria, Tex., the statements made refer especially to that locality. It must be borne in mind that latitude and altitude, as well as seasonal variations, will influence the limits of this period. In general, however, it may be said that hibernation begins at about the time of the first hard frost, and that it continues until the mean average temperature has been for some time above 60° F. In the spring of 1903 weevils left hibernation quarters at Victoria only when the mean average temperature had been for some time at about 68° F. While it is true that weevils if disturbed in hibernation are active at much lower temperatures than this, for some reason they do not leave the shelter of their hibernation places.

At Victoria, Tex., the average hibernation season may be said to extend from about December 1 to about April 1, or a period of about 4 months. In more northern latitudes hibernation will, as a rule, begin earlier and last later, covering a period of from 4 to 5 months.

APPARENTLY FAVORABLE CONDITIONS FOR HIBERNATION.

In December, 1902, a series of experiments was started to test the influence of various conditions upon the successful hibernation of weevils. Owing to the writer's absence from Victoria examinations could not be made at intervals, as would have been desirable. But at the middle of April, 1903, careful examinations were made to ascertain the shelter in which live weevils were found. In the preparation of hibernation jars several inches of dirt was placed at the bottom, and above that a variety of such rubbish as was thought might tempt the weevils to shelter. Dead banana leaves, hay, cotton leaves, dry bolls, squares, etc., were among the things used as rubbish. As several of these were placed in each jar the weevils had an opportunity to choose their shelter. Among the 39 which lived through the winter, 19 were found in the banana leaves, 7 in hay, 5 in dry cotton leaves, 4 were buried in dirt, 3 were on the surface of the soil, and 1 was hiding in an open boll. It appears, therefore, that 31, or 80 per cent of the 39 live weevils, were found in what may be termed "leaf rubbish." It was noted also that 25 of the survivors passed the winter out of doors in various locations, while 13 were under shelter indoors. Of the weevils placed out of doors all but one lot were protected from the rain. The 15 weevils contained in the jar which became wet all died, while but few of the jars which were dry failed to show a live weevil in the spring. Leaf rubbish and dryness appear to be favorable factors in successful hibernation.

PERCENTAGE OF WEEVILS HIBERNATING SUCCESSFULLY.

Naturally the percentage of weevils living through the winter will depend largely upon favorable climatic conditions and the accessibility of suitable shelter. It would be utterly impossible to determine this question under actual outdoor conditions, and our inferences must be drawn solely from percentages found to survive under cage conditions. In the laboratory tests referred to in the preceding topic 356 weevils were used. Of these, 240 were brought from the fields at the middle of December, 1902. Among these weevils, 38, or 15.8 per cent, survived. The remaining 116 weevils were all adult after September 25, 1902, and had been kept under observation in the laboratory. One single weevil, adult November 12, was the sole survivor of this lot. Since the weevils brought from the fields in the middle of December would be a correct average of those entering hibernating conditions, we may disregard the laboratory specimens in drawing our conclusions. The conditions offered would seem to have been favorable, and when this is the case out of doors it appears that about one in six of weevils found in the field at hibernation time may pass the winter successfully. This seems a very high percentage, but when we consider the numbers of hibernating weevils often occurring

upon young cotton in the spring it seems not improbable that during favorable seasons something like this percentage of the weevils finding favorable shelter will live. Of course, the percentage finding favorable shelter will be extremely variable, and it is in reducing the number and accessibility of favorable locations that the cotton planter has one of his very best opportunities to effect the destruction of a multitude of weevils, and thus greatly reduce the number which will emerge from hibernation and attack the crop of the following season. With shelter removed, cold and changeable weather will inevitably destroy many, and, in fact, most, of the weevils which would otherwise survive.

SEASONAL HISTORY.

EMERGENCE FROM HIBERNATION.

Emergence depends largely, as has been already shown, upon the mean average temperature prevailing. The presence of food does not seem to affect it. In the season of 1903 for one month preceding the emergence of weevils at Victoria the mean average temperature was 65.4° F. For the first two weeks of April it averaged 68.4° F. Weevils left their winter quarters from the middle to the last of April. While the mean average temperature for May was nearly 3° lower than the temperature prevailing at the time of emergence, weevils remained actively at work in the fields. In the fall also weevils remained at work at a lower temperature than that which seems to be necessary to draw them from their winter quarters. The reason for this fact is not apparent, but it is certain that once having left hibernation weevils will remain active at considerably lower temperatures. If the temperature becomes too low they remain quiet without taking food for long periods of time. If taken from their winter quarters weevils will be found active at ordinary day temperatures long before they would normally venture from their hiding places of their own accord. Weevils thus removed have been kept for a month without food or water, and they then assumed their normal activities when food was supplied to them.

After considerable search at San Diego in the spring of 1895, on April 27 Mr. Schwarz found the first specimens working upon seppa plants from roots which were then 2 years old. As the weevils first appeared in that locality in August, 1894, the number of hibernat ing weevils could not have been as great as in succeeding years, and consequently in the spring of 1895 hibernated specimens were "exceedingly rare." At Victoria, Tex., in the spring of 1902, Mr. Schwarz found the first weevils working upon volunteer plants on April 15. In the same locality the writer found, in 1903, that weevils left their winter quarters between April 10 and May 1. Evidence was found indicating that in some fields they began to move as early as March 28. At Calvert, Tex., also in 1903, Mr. Harris found the first

weevils working on cotton on April 12. At Victoria, in 1904, weevils were found in numbers upon seppa plants on March 14 and they were found moving in the field at intervals throughout the winter.

From these observations it appears that normal emergence takes place usually some time in April, whether the first or the last of the month depending largely upon the earliness of the season. Furthermore, the emergence of the first weevils may take place from two to four weeks before that of the last. In this fact lies one of the two great obstacles which prevent the successful application of poisons to the early cotton as a means of destroying the weevils. The second obstacle is explained on pages 41-43.

Owing to the empty condition of the alimentary canal, hibernated weevils are able to fly with ease, and this they must do in their search for food. Doubtless many perish soon after emergence, even if they find food which many others never succeed in reaching.

APPARENT DEPENDENCE OF REPRODUCTION UPON FOOD OBTAINED FROM SQUARES.

During the fall of 1902 a series of experiments, lasting for 12 weeks, was made to determine the length of life. of weevils fed solely upon leaves. In one lot, consisting of 9 males and 8 females, the average length of life of the females was 25 days, while that of the males was 36 days. Though this period far exceeded the normal time usually passed between the emergence of adults and the beginning of egg deposition, no eggs were found. Dissection of the females which lived longest showed that their ovaries were still in latent condition, though the weevils were then 81 days old. Few instances of copulation were observed among weevils fed upon leaves alone, and among nearly 70 weevils which were thus tested, no eggs were ever deposited. After a period of 3 weeks upon leaves, 11 weevils were transferred to squares. Females in this lot began to lay in 4 days, and 4 of them deposited 323 eggs in an average time of 20 days. The conclusion seems plain that so long as leaves alone are fed upon eggs do not develop, while a diet of squares leads to the development of eggs in about 4 days. It is worthy of note that the interval between the first feeding upon squares and the deposition of the first eggs is almost the same with these weevils taken in middle life as with weevils which have just emerged.

An examination of hibernated females taken in the spring of 1903, which had fed for 6 weeks upon cotton leaves, showed that their ovaries were still latent. Copulation was rarely observed among hibernated weevils until after squares had been given them. days after feeding upon squares, mating and oviposition began. The average period was from 3 to 5 days, and having once begun, oviposition continued regularly.

It has been found that food passes the alimentary canal in less than

24 hours. Assimilation, therefore, must be very rapid. It is evident that while leaves will sustain life certain nutritive elements found only in squares are essential in the production of eggs.

Upon dissecting weevils just taken from hibernation it was found that females contained no developed eggs, but that their ovaries were in an inactive condition, similar to those of females which had fed for months entirely upon leaves during the previous fall. Upon examining females taken from seppa cotton later in the spring, but before squares had appeared, it was found that they also were in similar condition. This was also true of females kept in the laboratory from the time of emergence from hibernation until squares became abundant, with only leaves for food. It seems peculiar that upon a purely leaf diet eggs are not developed, but all observations made indicate that this is the case. It can not be said definitely whether the females examined had been fertilized, but it is certain that they were not ready to deposit eggs.

PROGRESS OF INFESTATION IN FIELDS.

From among the many notes made upon this point the results of the study of two fields are here presented. The first field, consisting of about 15 acres, had been planted in cotton for several years and was closely surrounded by other cotton fields. The second field of 35 acres was upon newly broken land and situated in a comparatively isolated location.

Examinations were made frequently to determine approximately the percentage of infested squares present in various parts of these fields. The conditions of the examinations were made as uniform as was possible. The fields were divided into blocks, and practically the same ground was covered in each block upon succeeding examinations. TABLE XXII.-Progress of infestation, field 1.

The observations made in Block I cover a longer period, and are, therefore, more suggestive than those made in Block II. Evidently infestation began with the first appearance of squares. So long as the hibernated weevils alone were at work the percentage did not increase very rapidly, but with the advent of the second generation