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JOURNAL OF ECONOMIC ENTOMOLOGY 



[Vol. 7 



summarizing the effect of water on protoplasmic growth, says: "Water 

 plays a part in growth second in importance to no other agent, so that 

 in its absence growth cannot occur. As the quantity is increased, 

 growth is increased until an optimum is reached. The amount im- 

 bibed does not, however, depend directly upon the amount available, 

 but rather upon the needs and habits of the species." In summarizing 

 the effect of moisture on insect life we find Bachmetjew^ saying in 1907: 

 (1) that there is an optimum moisture for insect development; (2) that 

 this optimum is not the same for different species; (3) that the moisture 

 which may hasten the development of one species may retard the de- 

 velopment of another. 



To these conclusions the writer desires to add another — that the 

 rate of metabolism in certain actively feeding insects with an abundant 

 supply of succulent food is not affected by large differences in atmos- 

 pheric moisture. 



The material used in this study consisted of southern grain lice and 

 of chinch bugs infected and uninfected with the chinch-bug fungus. 

 In determining the effect of each percentage of atmospheric moisture 

 on the southern grain louse, ten specimens were carried from birth to 

 maturity. In working with the chinch bugs, a group of from twenty 

 to eighty was used for the determining of each point. The specimens 

 were taken from field or greenhouse (all chinch bugs came from the 

 fields) as the season dictated at the beginning of each experim.ent. In 

 all cases they were furnished with an abundance of succulent young 

 wheat for food. As the accompanying table shows, the southern grain 

 louse required six days to pass from birth to maturity under a con- 

 stant temperature of 80° F. and relative humidities of 37 per cent, 

 50 per cent, 70 per cent, 80 per cent, and 100 per cent. 



Subjection of eighty infected bugs from date of infection to day of 

 death under a constant temperature of 70° F. and percentages of at- 

 mospheric moisture of 40 per cent, 60 per cent, 80 per cent and 100 

 per cent, resulted in their death in nine or ten days. Subjection of 

 uninfected bugs, under the same constant temperature to the same 

 constant humidities, resulted in their death in eleven days. 



2 Bachmetjew, P., Experimentelle Entomologishe Studien, Zweiter Band, Sophia, 

 1907, p. 689. 



