430 



Journal of Agricultural Research 



Vol. XV, No. 8 



sents fairly natural conditions. Table II shows the extent of hibernation 

 occurring in the laboratory among fruit-fly puparia that were collected 

 during every month throughout the year. The greatest hibernation 

 occurred during the winter months commencing in December and the 

 least during the warmest months. As the data are secured from mate- 

 rial held in the laboratory in glass, the degree of hibernation is lower 

 than would obtain in the field normally, which is evidenced by the box 

 experiments. 



Table II. — Hibernation of Diachasma tryoni and D.fullawayi'^ 



Host puparia collected. 



1916 

 December 



1917 



January 



February 



March 



April 



May 



June 



July 



August 



September 



October 



November 



December 



Total 



number of 



parasitized 



puparia. 



302 



1,816 



774 

 i>599 



1,942 



925 

 1,263 

 1,605 

 2,946 

 I, 960 

 2,069 

 1, 116 



Number of 



D. iryoni 



emerging in 



normal time. 



193 



791 

 367 

 765 

 882 

 1,767 

 902 



1, 218 



1.356 



2, 821 



1,558 

 1,692 



744 



Number of 

 D.fullawayi 

 emerging in 

 normal time. 



83 

 120 



136 



153 



17 



41 



236 



81 



374 

 285 

 189 



Number of 

 Diachasma 

 larvae going 

 into hiber- 

 nation. 



99 



942 



287 



503 



37 



22 



6 



4 



13 



44 



28 



92 



Total 

 percentage of 

 hibernation. 



32.8 



51-9 



37-1 



31-5 



3-5 



I. I 



0.6 



0-3 

 0.8 



1-5 



1.4 



4.4 



16. 4 



o The ratio of hibernating larvaa of Diachasma tryoni is greater than is that of D. fullawayi, but just how 

 much greater as yet has not been determined. 



The greatest emergences of adults from hibernating individuals occurs 

 during the first seven months after the larva goes into hibernation. 

 From 78 1 larvae going into hibernation between August i, 191 6, and 

 July I, 1917, inclusive, 129, 119, 36, 67, 128, 147, 81, 27, 19, 16, 9, and 

 3 pupated and became adult during the period from the first to the 

 twelfth month, respectively. As the greater number began their 

 dormant period during the winter months and as the average duration 

 of this period is from two to six months, it follows that .the greatest 

 emergence from hibernating individuals occurs in the spring and early 

 summer months in Hawaii. 



No doubt more than one factor enters into the cause of hibernation 

 among the larvae of the two species of Diachasma. Cool" temperatures 

 seem the most important, as suggested in Table II. During August, 

 September, and October of 191 7 the total hibernation, as occurring in 

 material placed in glass vials, was 0.8, 1.5, and 1.4 per cent, respectively, 

 based upon records of 1,605, 2,946, and 1,960 parasitized puparia, respec- 

 tively. The average mean temperature at which this material was 

 kept during the three months was 78.7°, 74.7°, and 75° F., respectively. 



