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PROCEEDINGS OF THE NATIONAL, MUSEUM 



VOL. 84 



ing for an irregular circuit of the petri dish, but soon returning. It 

 turned its head doAvn so that the front of the head was parallel with 

 the plane of the paper and tore at the fibers with the serrate anterior 

 edge of the mandibles, frequently turning on its side to work to 

 better advantage. 



It paid no attention whatever to small spots caused by shadows. 



Reactions to light.— A. very brief study of the response of the wasp 

 to illumination by light of different wave length was made on the 

 first and second of April. This study was terminated all too sud- 

 denly by the death of the three insects — not as a result of the light 

 treatments given. The results are very interesting but cannot be 

 taken as conclusive because of the meager data obtained. They are 

 briefly recounted merely as suggestive of new lines of study. 



A quartz monochromator and mercury arc was used to supply 

 radiation of definite wave length. This instrument gave a strip of 

 light about 1 inch wide across the petri dish in which the insect was 

 confined. The intensities of each wave length used were adjusted 

 to equality, this value being 0.0005 watts to the square centimeter 

 (1/200 total sunlight intensity), which for the yellow light was 

 about 50 foot-candles. The white light was obtained from a 60- 

 watt bulb and a daylight filter, the filter being used to approximate 

 sunlight quality. 



The notes taken on the reaction of these insects to the various 

 illuminations are given in table 1. 



For equal incident energy of the different wave lengths it is seen 

 that the shorter wave lengths, violet and ultraviolet, consistently 

 give a greater stimulus to activity. Yellow and green hght give only 

 a weak stimulus. 



The shortest wave lengths used, 3,130 A, gave the greatest stimu- 

 lus — to the one insect subjected to it. The response to white light 

 was quite striking in comparison with that for the colored light. 

 In this case almost an equal response was observed for about one 

 one-hundredth the intensity of the colored light. 



Table 1. — Reactions of wasps (Odynerus tempiferus var. macio Bequaert) 



to light 



April 1, a. m. 



