98 THE BIOLOGY OF INSECTS 



in this connection. Bees are markedly phototropic, stimu- 

 lated by light, flying or crawling towards a definite source of 

 illumination. Minnich shows, however, that individual 

 variations may be apparent in their responses. Bees 

 generally turned rapidly so as to face, then crawled towards, 

 a '* directive " light, but only about a quarter of the number 

 whose course was carefully traced, made for the lamp in an 

 approximately straight Hne, the rest show^ed more or less 

 dcN-iation, and in a few cases the path was markedly indirect. 

 Out of seven bees tested on one occasion, six responded by 

 making directly for the source of light (Fig. 30, a-f). The 

 seventh on its first trial wandered around and away ; fourteen 

 minutes later it went by a less circuitous route away from 

 the light ; but a minute later, starting from a point 30 cm. 

 nearer to the lamp, it made for it though not in a straight 

 Hne (Fig. 30,^, //,/). "This example shows," comments 

 Minnich, '' that even the constant response of the bee to 

 directive illumination is not free from abrupt and apparently 

 inexplicable departures." Experiments with bees allowed 

 to wander in a uniformly illuminated area (" non-directive 

 light ") demonstrated much variation in their individual 

 beha\iour. '' The animal may turn markedly towards a 

 given side in one trial, and in the next turn quite as markedly 

 towards the opposite side. Again, the direction of turning 

 may be completely changed several times in the course of 

 a single trial." It seems clear, therefore, that the reaction 

 of at least some hive-bees to visual stimulation is not so 

 fixed as to be absolutely predictable. The bee may comince 

 the obser\^er that she is alive by behaving sometimes in an 

 unexpected manner. 



A set of experiments performed by Minnich on bees 

 with one eye blackened over so as to be impervious to light 

 or almost so, is of ver}' special interest. Many observers 

 have tried similar experiments with various insects, and find 

 that their reaction to directive light is to " loop " towards 

 the side on which the eye is still functional. INIinnich 

 showed that some of the bees subjected to such treatment 

 learned by experience to modify this reaction so that their 



