EXPEEIMENT STATION EEPOET. 571 



For Hightstown the temperature varied from a maximum of 82° to 

 a minimum of 24°, all within a space of three days, but the mean 

 maximum was about 63° and the mean minimum was about 36°. On 

 no day was the minimum temperature as high as 60°. Turning now 

 to our bog records at Jamesburg, 60° at a two- foot depth was recorded 

 April 25th and May 1st, and 61° May 6th. At a one-foot depth one 

 degree higher was recorded on the dates given. On the White bog 

 63° was recorded at one-foot depth, and 62.5° at two- foot depth, May 

 10th. Very similar temperatures for corresponding dates were re- 

 corded by Mr. Budd and Mr. Eider. In other words, the same actual 

 average temperature was reached in the water a very little later than 

 in the air. There was less fluctuation and the warm temperature was 

 continuous, promoting a slow, equal development. On the other hand, 

 the direct influence of the sun and the stimulation of extreme tempera- 

 tures undoubtedly promoted more rapid growth, as indicated by the 

 fact that the first larvae were found where the vines themselves were 

 already most advanced. The large number of collapsed eggs found 

 after the water had been drawn indicates that the direct effect of the 

 warm water is such as to destroy the vitality of the ovum, but the fact 

 that I secured sound eggs from below the surface in March, indicates 

 that the water covering only was not at fault. No eggs that had 

 hatched under water were secured this season, but in previous seasons 

 I have found such not infrequently. 



CONCLUSIONS. 



May 1st, in a normal season, may be safely assumed as the date 

 when all the eggs of the Eudemis have hatched on vines that have been 

 uncovered all winter. 



A normal season in the cranberry regions of New Jersey is one in 

 which the mean day temperature during April has reached or only 

 slightly exceeded 62°. 



Eggs on vines covered by water are in an unnatural position, and, 

 while they maintain their vitality during the winter, they begin to 

 lose it when the water reaches a temperature approaching 60°, espe- 

 cially where the covering is eighteen inches or more. 



Vines covered with less than six inches of water are affected by 

 the surface conditions, and eggs will develop or die within a few days 

 after they do on uncovered vines. May 5th may be ordinarily con- 



