SPIDERS AND INSECTS OTHER THAN ANTS 381 



periment yielded the same result. Hence Holmes logically con- 

 cludes that the direction of the rays of light is a factor in de- 

 termining the direction of the movements. Whenever a shadow 

 was cast upon a larval mosquito, even when the shadow was 

 cast by an object beneath the aquarium, the larva always moved 

 downwards and away from the light. When shadows were cast 

 upon larvae resting on the bottom of the jar, commotion was 

 produced, but no definitely directed movements. A series of 

 experiments conducted with larvae of all ages demonstrated 

 great variation in their phototactic response, and that the 

 variations are not due to age. Some were indifferent, some 

 moved towards the light, and some moved away from the light ; 

 but all responded to shadows in the manner mentioned above. 

 Since the. larvae always dart downwards and away from the 

 light, no matter from what direction the shadow comes, Holmes 

 concludes that this characteristic retreat of the larvae is not a 

 tropism, but a specific response to shadows. Evidently this is 

 an example of what Bohn would call differential sensibility, and 

 what less conservative writers would term an exhibition of fear. 



According to the same investigator (30), the adult mosquitoes 

 display a peculiar combination of responses to light, but are more 

 apt to settle on dark than on light objects; and during the day 

 they seek the shade even when it is neither hot nor dry. At 

 night they sometimes fly towards the light. The adults of some 

 species show marked positive phototaxis. Eating a full meal 

 does not alter the phototactic response. 



C. H. Turner (58) has conducted a series of experiments to 

 test the response of certain parasitic bees of the family Stelidae 

 to light. The bees were confined in a rectangular wire cage 

 sixteen inches high, twelve inches long and twelve wide. To 

 keep them in a physiologically normal condition, they were 

 supplied with honey and with water. Record was kept of their 

 behavior under the following conditions: when all sides of the 

 cage were exposed to diffuse daylight, when one side of the 

 cage was exposed to the oblique rays of direct sunlight, when 

 the top and two sides of the cage were exposed to such rays, 

 when such rays were admitted only through the upper or lower 

 half of one side, when a narrow beam of electric light was passed 

 through the cage in such a manner as not to impinge upon any 

 of the inmates, etc. The experiments demonstrated that, when 



