REACTIONS OF THE MASON WASP TO LIGHT 361 



these random movements were for the purpose of escaping 

 from the cage is evidenced by the fact that whenever I made 

 a small opening, whether in the bright light or in the shadow, 

 whether in the side towards the source of the light or in some 

 other side, one or more wasps always escaped or attempted 

 to escape. 



Responses to Shadows. In some experiments performed with 

 some parasitic bees 4 which displayed a pronounced tendency 

 to move towards the source of the light it was noticed that 

 bees climbing upwards through the sunlight, on reaching a 

 shadow, almost invariably dropped backwards. Careful obser- 

 vations were made to see if these wasps, which did not exhibit 

 a pronounced tendency to move towards the source of the 

 light, responded in the same manner to shadows encountered 

 under similar conditions. As a rule, when these wasps reached 

 the shadow they either moved on into it or else turned through 

 an angle of 90 degrees and walked along the border line between 

 the light and shadow. In a few cases, less than three per cent 

 of those observed, the wasps dropped back when they reached 

 the shadow. 



Responses to Hues. Numerous experiments with colored lights, 

 a few of which have been recorded under series IV, were con- 

 ducted, not to test the visual powers of wasps, but to ascertain 

 if certain rays stimulated a stronger response than other rays. 

 As to the effect of hues as such the experiments were noncom- 

 mital. The brightness content, however, seemed to play an 

 important role. When a light stimulus, no matter what the 

 hue, followed one with a lesser brightness content, the wasps 

 usually became active; but when it followed one of greater 

 brightness content the wasps usually became inactive. The 

 orange was the most transparent glass, the blue next and the 

 ruby least. Whether the orange followed twilight brightness, or 

 the blue or the ruby, it usually stimulated the wasps to action. 

 Unfortunately no experiments were made with the orange 

 following a bright white light. When the ruby followed twi- 

 light darkness (Exp. 14) usually the wasps were stimulated 

 to activity; but when it followed a bright white light (Exp. 18) 

 or a blue light (Exp. 21) the wasps usually became quiet. When 

 the blue light followed a bright white light (Exp. 6, 8, 10), in 



4 Journal of Animal Behavior, 1911, Vol. 1, pp. 374-392. 



