February, '17] headlee: humidity and metabolism 31 



SOME FACTS RELATIVE TO THE INFLUENCE OF ATMOS- 

 PHERIC HUMIDITY ON INSECT METABOLISM 



By Thomas J. Headlee, Ph. D., New Brunswick, N. J. 



The effect of atmospheric moisture (water vapor) upon the speed 

 of insect metabohsm is seeminglj^ extremely variable. It has been 

 shown that moist air retards in some cases the development of the 

 eggs of Dendrolimus pini^ while in other cases it seems to hasten it. 

 Moist air hastens the development of the larvae (change from larva to 

 pupa) of Mayetiola destructor^ and dry air greatly retards it. Dry air 

 retards the development of the pupa of Lygellus epilachnce^ and hastens 

 that of Pieris hrassica-^. Moist air is injurious to the adults of Dor- 

 cadion sturmiv' but highly favorable to plant lice. Dry air, even when 

 warm, causes lethargy in Phytodecta viminalis^ and several other 

 species.^ Neither dry nor moist air materially affects the speed of 

 metabolism in Toxoptera graminum when feeding on young and suc- 

 culent wheat. ^ 



The writer undertook the study of the response of the various stages 

 of the bean weevil (Bruchus obtectus Say) for the purpose of finding 

 out to what extent the variations of speed of metabolism in response 

 to atmospheric humidity held true in a single species entirely depend- 

 ent upon metabolic water and for the purpose of deriving data that 

 might lead to the underlying cause of the response. 



Realizing the extent to which factors such as temperature and light 

 would interfere with the results and having an idea that the presence 

 of carbon dioxide and oxygen might influence the results, an effort 

 was made to eliminate them as variables. All insects were kept at a 

 practically constant temperature of 80° F. ; all were kept in complete 

 darkness; all were subjected to a passing stream of air, the minimum 



1 Serebrjanikaw, A. W., Nachr. des Forst. Instit. zu St. Petersburg, VII., p. 29-102, 

 1901. 



2 Headlee, Thos. J., and Parker, J. B., Bull. No. 188, Kans. St. Agr. Expt. Station, 

 p. 107-109, 1913. 



5 Giard, A., La methode experimentale dans I'Entomologie, Bull. Soc. France No. 

 4, p. 57-63, 1896. 



* Urech, Friedr., Chemisch-Analytische Untersuchungen an lebenden Raupen 

 Puppen xmd Schmetterlingen und ihren secreten, Zoolog. Anz. 1890, No. 335, p. 

 254-262, No. 336, p. 272-280, No. 337, p. 309-314, No. 338, p. 335-345. 



^ Bachmetjew, P., Experimentelle Entomologische Studien, Band 11, p. 574, 1907. 



^ Kolbe, H. S., Einfiirung in der Kenntnis der Insekten, 1889-1893. 



^ Bachmetjew, P., 1. c, p. 688. 



8 Headlee, Thos. J., Jour. Ec. Ent., Vol. VII, No. 6, p. 416. 1914 



