WEATHER AND CHANGE IN WEIGHT OF BEE COLONY 29 



with an increase in temperature, the permeability of the protoplasts 

 of the multicellular secreting hairs which cover the nectary of Abu- 

 tilon rapidly increases. The osmotic pressures (intimately related 

 to permeability in plants) of aqueous sucrose solutions were like- 

 wise found by Morse, as cited by Stiles (82)?to vary directly with 

 temperature, at temperatures generally encountered in working with 

 plants. With the effect of low temperatures upon the accumulation 

 of sugar on the one hand, and the effect of high temperatures upon 

 permeability on the other, Kenoyer states that the evidence points 

 to the conclusion that the secretion of nectar results from a balance 

 "between the two, and that the optimum temperature for secretion 

 may be represented by the point where the negative graph repre- 

 senting temperature and sugar accumulation crosses the positive 

 graph of permeability of protoplasts to sugar and temperature. 



Phillips and Demuth (31), in referring to white clover (Trifolium 

 ■re pens), state that this species of Leguminosae may rarely be counted 

 upon as a major honey source where the average summer tempera- 

 ture exceeds 75° F. (23.9° C), and a more important consideration 

 is that secretion is most rapid where there is a considerable daily 

 range of temperature, the best results being observed when the night 

 temperature is below 65° F. (18.3° C), and the day temperature 

 above that. The slight difference between Kenoyer's optimum tem- 

 perature and the observations of Phillips and Demuth may be 

 •explained by the fact that the former was studying nectar secretion 

 while the latter were referring to conditions as measured by the 

 honey crop. 



There are numerous records where low temperatures appear to 

 have an important bearing upon nectar secretion. On the other 

 hand, the literature of beekeeping contains many references, mainly 

 observations by beekeepers, to the effect that high temperatures are 

 necessary for an abundant secretion of nectar. Undoubtedly the 

 physiological behavior of plants in nectar secretion varies somewhat 

 with different species and under varying climatic conditions. Like 

 Ono (26) , Wilson (33) found that temperature makes but little dif- 

 ference in nectar production. In the case of branches of Prunus 

 laurocerasus , however, he discovered that a temperature of at least 

 12° C. (53.6° F.) is necessary for the metamorphosis of the cell walls 

 and the raising of the cuticle, and that after this activity of the nec- 

 tary had passed a much lower temperature sufficed for continued 

 secretion. Haupt (17) found that a certain minimum temperature 

 was necessary to induce secretion and Demuth (9), in making obser- 

 vations to determine the temperature at which basswood (Tilia 

 americana) begins to yield nectar, found that in northern Indiana 

 this plant did not yield nectar until a temperature of 64° F. (17.8° 

 C.) was reached. 



From what has preceded, it is quite evident that considerable con- 

 fusion exists regarding the true relation of temperature either to 

 nectar secretion or to changes in colony weight. Much of this con- 

 fusion is undoubtedly duo to a lack of sufficient discrimination be- 

 tween the uses of the terms "nectar secretion" and "change in 

 colony weight." So far as the changes in weight are concerned, the 

 majority of the data indicate that during a honey flow the relation 

 of these changes to temperature is positive. If there does exist a 

 negative correlation between nectar secretion and temperature, it 



