365 



of low ;itni'-|>licii( humidity, other stages arc unfa\ orahly 

 "W atmo-pherir moisture mi.L'hl be developed into ;m efl 



icide for certain I <^rain b 



Eclosion. Moisture frequently determines the time 

 or tin* emen" mm the pupa. Median lli< 



emerge from tlie puparia in dry weather, hut issue in abundaiH e after 

 rainfall in (he proper B6880n. When bred indoors, I lie tli<- do not 

 emerge from dry >oil, even though the temperature he favorahle, hut 

 emerge shortly when the soil is moistened. 



Activity. Wet weather lessens the activities of insects exposed to 

 I here are some exceptions, however. Larvae of the midges, Itoni- 

 dida\ are all very sensitive to the presence of moisture, to which they 

 positively. Larva? of the clover seed midge emerge from the clo- 

 ver heads usually in damp weather and often in large numbers when the 

 plants are wet with rain. Even when full grown and contracted in 

 readiness to form the puparium, they revive and move about if mois- 

 tened with water. 



Oviposition. It has been found that with the house fly, when 

 temperatures are high or moderately high, increased humidity hastens 

 egg-laying. This may be partially due to the effect of humidity on 

 the food and breeding substances keeping them moist and attractive. 

 (Bishopp, Dove, Parman.) 



Mortality. Changes in relative humidity produce striking changes 

 in the mortality of Drosophila, the mortality increasing with a decrease 

 of humidity, the optimum humidity being 100 per cent. The effects 

 of low humidity on mortality are most marked with very young pupa?, 

 whose covering permits a rapid evaporation of body moisture. After 

 a few hours, when integumental changes making evaporation more 

 difficult have set in, the effects of low humidity are correspondingly 

 decreased. (A. Elwyn.) 



Hibernation. As a preparation for hibernation, the water content 

 of an organism is frequently reduced; as also in seeds or spores. Thus 

 the Colorado potato beetle loses about 30 per cent, of its gross weight 

 through the loss of water, which enables it to withstand a lower freezing 

 point and higher temperatures than if the protoplasm were not thus 

 condensed. (Tower.) As Sanderson notes, the time of emergence from 

 hibernation is controlled by moisture conditions as well as temperature, 

 or independent of temperature. Tower kept potato beetles for eight- 

 een months at a high temperature, but with a dry atmosphere, and 

 they emerged as soon as normal moisture conditions were produced. 



