growth of larvæ within, thus producing quickly a large number of weevils ready to do further injury.

It is still an open question as to how low winter temperatures the weevil can withstand. It is certain that in southern Texas many larvæ and pupa slowly continue their development during the winter season. Mr. S. G. Borden, of Sharpsburg, Tex., in a letter written January 27, 1896, says: "Hands clearing up cotton stalks report plenty of the larvæ in dry bolls." Mr. Schwarz found weevils hibernating in all stages, except the egg, at Victoria, Tex., during Febru ary, 1902. At the same locality in January and February of 1904, the weevils in larval, pupal, and adult stages were taken alive from dry bolls by Mr. J. D. Mitchell, a resident and cotton planter of that place. After the weevils first made their appearance at San Antonio in the fall of 1895 they were supposed to have been entirely destroyed by frosts during the following winter. The lowest temperature recorded at San Antonio for that winter was 26° F. on December 30, 1895. On January 2, 1896, Professor Townsend made an examination of the condition of the weevil, and, so far as he found, all larvæ in bolls were then dead, while pupa and adults were all alive. In spite of the mildness of the remainder of the winter the weevils did no damage to the crop of 1896, and were not found in fields in which they were present the year before. In writing of this unexpected condition, on October 19, 1896, Professor Townsend says, "The timely drought of last of May and first of June is what killed the weevils this year." There is therefore some doubt as to whether frosts or drought were responsible for the destruction of the weevils at San Antonio in 1896.

At Victoria, on February 17, 1903, the lowest temperature recorded by the Weather Bureau report was 20° F., but many weevils hibernated successfully. Doubtless much lower temperatures than this were experienced in more northern localities in the weevil belt, but in no place have the weevils been exterminated thereby.

EFFECT OF RAINS UPON DEVELOPMENT OF WEEVILS.

While it is a mistaken idea that rains first bring the weevils, it is true that they favor weevil increase in several ways. Frequent rains increase the growth of the plant and lead to the production of a larger number of squares which may become infested. Driving rains knock off infested squares, and by softening and moistening the food hasten the development of the larvæ within. Squares which are already upon the ground are protected during rainy weather from sunshine and drying. Rain hinders the enemies of the weevil far more than it does the development of the weevils themselves. In several such ways rains contribute directly or indirectly to the more rapid multiplication of weevils and cause the common impression among cotton planters alluded to above.

EFFECT OF WET WINTER WEATHER ON HIBERNATING WEEVILS.

Owing to the writers' absence from Victoria during the winter months, observations could not be made directly or immediately upon this point. It was found, however, that all weevils in hibernation tests which passed the winter successfully had been kept dry. The winter of 1902-3 was unusually wet at Victoria, and the number of hibernated weevils which were to be found on early cotton plants was noticeably less than during previous seasons which had been dry. It seems probable, therefore, that as many weevils perish from frequent wetting as from exposure to the cold.

EFFECTS OF OVERFLOWS IN FIELDS.

Unusually favorable conditions for these observations were obtained at Victoria in the season of 1903. During the latter part of February an overflow of the Guadalupe River covered many of the cotton fields along its course. The fields in which especial study was made were wholly submerged from one to several days. Cotton was planted in some of these fields between March 15 and 17. Owing to cold weather the growth of the plants was delayed and squaring did not begin until between May 10 and 17. Immediately after this date it was found that weevils were present and at work, and fallen squares were first found about May 23. From a study of this field it became apparent that the overflow had caused a considerably less decrease than had been anticipated in the number of hibernating weevils. Possibly the fact that the winter of 1902-3 had been exceptionally rainy may account for the lack of contrast in weevil abundance in overflowed fields and those which did not suffer in this way since, as has already been noted, hibernated weevils were unusually scarce, even on uplands.

Another period of high water occurred during the last of June and the first of July and gave a convenient opportunity to note its effect upon active weevils. Many fields were partially and some wholly submerged. This condition lasted for several days. Examination made after the recession of the water showed that many fallen squares which had certainly been in the water for some time contained uninjured larvæ and pupæ. Naturally eggs and larvæ found in squares upon the plants, even though under water for some time, escaped unharmed. Weevils were working normally upon the plants. No diminution in their numbers could be seen and it was apparent that the overflow caused no check either to the development of the immature stages or to the activity of the adults. These observations emphasize the fact that the weevil can not be drowned

out.

LABORATORY OBSERVATIONS UPON TIME WEEVILS WILL FLOAT OR ENDURE SUBMERGENCE.

These tests were divided into two parts, each of which includes both the immature and mature stages. In each part floating and submergence were tested.

Sixty squares, believed from external examination to be infested, were floated in a driving rain for six hours. They were then removed and left for several days, during which time 75 per cent of them produced normal adults. Ten squares which were floated in driving rain for six hours were opened at once, and in every case found to be but slightly wet upon the inside. These contained 6 larvæ and 4 pupæ, and all were in perfect condition.

As squares float normally, submergence tests were considered extreme. Five squares were submerged for six hours, and after that produced 3 normal adults; 1 pupa died, and 1 square was found to have been uninfested. Five more squares were submerged for thirtyone hours. These produced 2 normal adults, and 1 pupa died in the process of molting after removal from the square. Death was probably caused in the last case by drying; 1 square was found to contain a dead pupa, and 1 was not infested. To test the possibility of its living, should the square be penetrated by water, a naked pupa was submerged for six hours, but in spite of this unusual treatment it produced a normal adult.

In the tests made upon the floating power of adults, weevils were isolated and placed in water in tumblers. They were dropped from a considerable distance above the surface, so that they became entirely submerged, and then floated to the surface naturally. The surface tension of the water was found to be sufficient to float weevils which were placed upon it carefully. The generally hairy condition of the surface of the weevil's body prevents its being readily wetted, so that it may struggle for some time in the water without becoming really wet. When dropped in this way weevils float head downward, with the tip of the abdomen above the surface. In the submergence tests weevils were held down by a wire screen, and all bubbles were removed from their bodies by a pipette, thus making the tests as severe as possible.

TABLE XXVI-Effects of floating and submergence on all stages.

In the case of squares floating normally it is evident that they might remain in water for several days without injury to the weevil within. Very slight wetting of the cell takes place even under the extreme conditions of submergence. The effect of a brief flood would not, therefore, be at all injurious. As adults float as readily as do squares, they may also be carried long distances, and, furthermore, they are able to crawl out of the water onto any bushes, weeds, or rubbish which they may touch. Even when floating for several days continuously they are able to live and may be carried directly to new fields. The floating of adults and infested squares explains the appearance of weevils in great numbers along high-water line immediately after a flood, and indicates that probably the most rapid advance the pest will make in the United States will be into the fertile cotton lands of the Red River Valley in Louisiana.

PROBABILITIES AS TO THE INFLUENCE OF CLIMATE ON THE WEEVIL IN COTTON REGIONS NOT NOW INFESTED.

The influence which the lower temperature prevailing over the northern edge of the cotton belt may have upon the development, destructiveness, and spread of the weevil is as yet largely problematical. No considerable amount of accurate data upon the development of the weevil being at present available except that collected at Victoria, Tex., during the seasons of 1902 and 1903, it is impossible to predict with certainty how far or how rapidly the weevil may spread or the rapidity of development which may take place under the different climatic conditions prevailing in regions not at present infested, or whether it may be expected that its destructiveness to cotton will be materially reduced in other sections. These questions are, however, of considerable interest because of the probability that the

weevil will ultimately spread over the entire cotton belt in spite of any measures which may be adopted to retard its progress.

During the past century the attention of many botanists and zoologists has been drawn to the relations existing between geographic areas and the distribution of plants and animals. In this country the limits of the well-defined zones and the laws governing the distribution of plant and animal life through those zones have been most carefully determined by Dr. C. Hart Merriam, Chief of the Division of Biological Survey of the United States Department of Agriculture." A few years before the publication of Doctor Merriam's completed results Dr. L. O. Howard, Chief of the Division of Entomology, first applied the principles underlying geographic distribution to a study of the probable spread of a number of species of very injurious insects, most of which had been imported into this country, and recently he has made a more extensive study of a very practical nature concerning the geographic distribution of the yellow fever mosquito. Many observations have shown that in general the limits of the spread of an imported insect pest may thus be approximately determined. It is, therefore, not out of place to consider at this time some points in regard to the probable status of the boll weevil in the cotton belt outside of Texas.

According to the map published by Doctor Merriam, the entire cotton-growing area of the United States lies within the Lower Austral Zone, the northern limit of which is marked by the isothermal line showing a sum of normal positive temperatures (above 32° F.) amounting to 18,000° F. The weevil has already become established near Sherman, Tex. As nearly as can be told from data at present available, the isothermal line passing through Sherman, if extended eastward, would pass along the Red River Valley, through the extreme southern part of Arkansas, across central Mississippi and Alabama, a little south of Atlanta, Ga., and thence curve northeastward through South and North Carolina. It therefore becomes evident that "temperature" will not prevent the spread of the weevil eastward. Even if it should not go beyond the isothermal line within which it now thrives, its territory would still include most of the great cotton belt of the United States. Furthermore, there is no evidence to show that the weevil has yet reached its most northern limit, and the probabilty remains that it may yet show itself capable of existing anywhere within the Lower Austral Zone where cotton can be grown.

A comparison of the positive temperatures of various localities in the

a Bulletin 10, U. S. Dept. Agr., Division of Biological Survey, Life Zones and Crop Zones of the United States.

Proc. Entom. Soc. Washington, Vol. III, No. 4, pp. 219-226. "Notes on the Geographic Distribution in the United States of Certain Insects Injurious to Cultivated Crops.".

Treasury Department-Public Health Reports, Vol. XVIII, No. 46. "Con- ̧ cerning the Geographic Distribution of the Yellow Fever Mosquito.”