84 REPORT 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 



Kor have we to deal with the cold rains that characterize the South- 

 ern winter, and sometimes occur as late as the beginning of May. The 

 influence of this weather on the hibernating moth has not been defi- 

 nitely ascertained, but it is more than probable that, when occurring late 

 in spring, especially if accompanied by a "norther,'' it may prove as in- 

 jurious to the first generation of worms as it is known to be to the cot- 

 ton plant. We have to deal rather with that broiling and humid state 

 of the atmosphere consequent upon frequent showers and a clouded sky 

 during the summer months or later. The earth may be said to steam, 

 and the air is full of vapor. The influence of such weather is twofold, 

 viz., direct and indirect. 



Its direct influences may, perhaps, best be illustrated by citing, in 

 contrast, the effects of dry weather, which effects we have repeatedly 

 had excellent opportunities of watching and studying. As witnessed 

 in the field, a large portion of the eggs during dry weather actually 

 desiccate and fail to hatch. The worms are less active, and wanting 

 in vitality; they drop more easily to the ground, and are so affected by 

 the dry, heated surface that, in almost every instance, they fail to regain 

 the plant. While vigor and vitality are thus impaired, the development 

 during such weather is unduly hastened. The worms, for the most part, 

 web up prematurely and fail to effect the change to chrysalis, generally 

 dying in the act, half- worm, half-chrysalis. The chrysalides, in case the 

 transformation was successful, show a great tendency to rot, while the 

 moths, which hatch from the comx)aratively few that remain sound, find 

 scarcely any food in the cotton field, as the glands, already described 

 (p. 10), are almost entirely wanting in honey during very dry weather, 

 i^ourishment and fecundity being correlated, it is more than probable 

 that the moths, poorly nourished, will lay fewer eggs under such cir- 

 cumstances. All the effects described are intensified and become most 

 marked during extreme drought, so that frequently at the end of a dry 

 spell, such as is not infrequent in July and early August, not a worm 

 can be found. A rainy season, following such a spell, will produce a 

 most noticeable change. Its effects are almost magical. The plants 

 freshen up, and the moths simultaneously become active ; their eggs 

 hatch freely, and the worms are so voracious and active that they soon 

 destroy the new leaves or " top crop" and then, of necessity, work on the 

 older ones. 



The effects of dryness, as here described, are equally noticeable when 

 produced artificially. Experiments upon plants growing in the field, 

 but inclosed in muslin-covered frames, have produced all the unhealthy 

 conditions of the insect, simply because the covering prevented the nor- 

 mal precipitations of dew upon the plants ; while in vivaria the injurious 

 effects of a dry atmosphere have been equally noticeable. In the dry, 

 hot air of the Bahamas the worms are reported as often dying from the 

 heat in numbers on the plant ; a fact which would indicate that our 

 climate is more favorable to their welfare than that of those islands ; 



