52 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 1 



The possibility of controlling Bruchids in stored cow-peas was 

 shown in 1905 by Mr. J. W. T. Duvel.^ 



Prof. E. D. Sanderson in 1905 proposed a hypothesis regarding 

 the determination of the time of maximum emergence from hiberna- 

 tion of the cotton boll weevil.^ The proposed rule was based upon 

 the departure of the temperature from the normal. The maximum 

 emergence Avould be later or earlier than the normal time as the 

 accumulated temperature would be lower or higher. The work on 

 the boll weevil has furnished another example. Mr. W. 0. Martin, 

 formerly associated with Mr. Wilmon Newell, devised an ingenious 

 method of determining the time when weevils in the dispersion move- 

 ment had arrived in any certain field.' Previously it has been shown 

 by Dr. W. E. Hinds and the writer that the growth of the weevil 

 larva was regulated practically absolutely by effective temperatures 

 and the amount of temperature necessary for the development of the 

 different stages has been determined. Therefore the age of any 

 weevil stage found in degrees of effective temperature was known. 

 It only remained to sum up the daily effective temperature, going 

 backward from the day upon which the specimens might be found 

 until the total equalled the known amount necessary for that stage. 

 The date thus obtained, of course, was the one upon which the parent 

 weevil had reached the field. 



There are two respects in which the cattle tick is conspicuously 

 affected by temperatures: (1) its distribution in this country is lim- 

 ited; and (2) in a large portion of the natural range the eggs while 

 not destroyed are prevented from hatching for several months during 

 the winter. Attention was called by Doctor Howard to the restricted 

 distribution of the tick and the close correspondence of its range to 

 that of the yellow fever mosquito. In the present paper, however, 

 we are concerned with the second feature, namely, the long deferred 

 hatching due to low temperatures. 



In work relating to the cattle tick, in which the writer is associated 

 with Mr. W. A. Hooker, it was found that the total effective tem- 

 perature required for hatching varied from 840 to 1510 degrees F. 

 The shortest incubation period was found when the accumulated 

 effective temperature was highest and the longest incubation when 

 the accumulated effective temperature was lowest. That is, the incu- 

 bation period varied inversely with the accumulated effective tem- 

 perature. Now, obviously the reason for the variation is the daily 

 mean temperature. In other words, incubation takes longer in winter 

 than in summer. What was desired then was to determine the rela- 



dBul. Bur. Ent. 52, p. 29-42. eBuI. Bur. Ent. 54, p. 49-54. 



fCir. La. Crop Pest Comm. 9, p. 23-27. 



