20 



BULLETIN 1339, TJ. S. DEPARTMENT OF AGRICULTURE 



increases in weight were recorded during 136.4 hours. In May, 1923, 

 during the honey flow there were 138.5 hours of sunshine, while colony 

 2 made gains during 137.5 hours. The similarity between the hours 

 of sunshine and hours in which gains were made are somewhat of a 

 coincidence, for, as stated, gains are sometimes made in cloudy hours 

 and gains are not made in all hours of sunshine. The effect of sun- 

 shine upon net gain will be discussed later (p. 36) . 





^?4* 



3& 

 FIG. 8 



Graphs of average hourly weight changes, temperature, relative humidity, and total hours of 

 sunshine. Colony 2, spring period 



The temperature at the time when the colony ceases to gain in 

 weight at the close of the day (figs. 7 and 8) is well above that at 

 which bees are able to engage in effective outside work. This is 

 shown by the fact that the average temperatures at the time of the 

 morning loss, due to flights, are much lower than the temperatures 



