392 DWIGHT E. MINNICH 



1. Continuous factors 



a. Temperature and humidity. Of the continuously operative 

 factors, none are more important than the general conditions of 

 temperature and humidity. These profoundly affect the activity 

 of bees. Mclndoo ('14, p. 279) says: "Climatic conditions per- 

 ceptibly affect the activity of bees. When it is extremely warm, 

 they are most active and are rarely quiet even for a few seconds. 

 When it is moderately warm, they are less restless, and when 

 rather cool, bees do not move freely." Again he says: "During 

 cool weather their movements are quite sluggish, and when the 

 humidity is high they are much less active and respond to vari- 

 ous odors more slowly than when there is low humidity." 



Precisely the same effects were noted in the present experi- 

 ments. So serious did they become on several occasions that the 

 experiment had to be abandoned. On cool, damp days bees 

 were apt to be quite unreactive, and prolonged exposure to light 

 often failed to induce locomotion. Considerable mechanical stim- 

 ulation might call forth creeping, but it was of desultory kind 

 and was apparently unaffected by photic stimulation. There can 

 be no doubt, therefore, that general weather conditions consid- 

 erably affect the behavior of bees toward light. Since some 

 experiments were continued under less favorable weather con- 

 ditions, it is quite probable that they account for some of the 

 aberrancies observed. 



b. After-effects. In making quantitative determinations in 

 non-directive hght, trials were frequently made in the two inten- 

 sities in rapid succession. Although the bee was always exposed 

 for at least thirty seconds to a given intensity before making a 

 test, there still existed the possibility that an after effect of the first 

 intensity might influence the behavior of the animal in the sec- 

 ond. Thus Herms ('11, p. 215) has demonstrated an after-effect 

 of photic stimulation in the blow-fly larva, which may manifest 

 itself in the continued orientation of the animal for as much as 

 fifteen to twenty seconds after the cessation of the stimulus. 

 That such is not the case for bees, however, is very clearly dem- 

 -onstrated by the following experiment. 



