EARLY EXPERIMENTS OF PLATEAU AND OTHERS. 143 



disk in the place formerly occupied by the blue one, and paying no heed 

 to the latter at one side. On the other hand, when the disk is moved a 

 foot from the former place, the wasp is usually unable to find it, while 

 the bee locates it quickly by the color. The fact that wasps guide them- 

 selves so well when deprived of antennae, without distinguishing colors 

 very clearly, is one of the best proofs that they see the forms and contours 

 of objects, further evidence being afforded by the fact that they can not 

 direct themselves when their eyes are covered with varnish. 



Response of wasps to color. — In their classic experiments with wasps 

 (1887:105), the Peckhams carried out experiments upon the response to 

 color, largely with the idea of verifying Lubbock's conclusions. Their 

 results were somewhat at variance with his, however, as they tended to 

 prove that wasps rely very greatly upon color for their guidance. This 

 divergence may be explained in part by the fact that they worked with 

 large numbers, 500 sometimes passing into and out of the nest in 5 minutes, 

 and that the presence of two observers increased the accuracy. At the 

 outset a hole 4.5 inches in diameter was cut in a sheet of bright-red paper 

 about 24 by 20 inches in extent, and the latter was placed above the nest 

 in such a way that the entrance was not at all impeded and could be plainly 

 seen from above. The returning wasps did not enter, but circled over the 

 paper, seeming greatly excited, until one more intelligent or venturesome 

 flew in and the others gradually followed. In the course of 3 hours all of 

 them became accustomed to the paper and worked as usual. Two days 

 later a blue paper was substituted and this produced as much confusion 

 as before, though the wasps became used to it in a little more than 2 hours. 

 The next day the blue paper was removed and a cage full of wasps released 

 at some distance; an hour afterward 25 or 30 wasps were found buzzing 

 about, apparently not knowing how to get into the nest, though they en- 

 tered at once as soon as the blue paper was replaced. When a yellow paper 

 was substituted for the blue, 130 wasps noticed the change within a period 

 of 10 minutes, circling around the nest several times before entering, while 

 8 seemed not to notice it. After an hour's exposure, 70 out of 100 wasps 

 recognized the change, but after the paper had been over the nest for 3 

 working hours, only 8 out of 200 hesitated before entering. The sub- 

 stitution of a light-green paper with yellowish reflections for the yellow one 

 produced a response, but it was not nearly so marked, 100 out of 172 

 wasps noting it, but to a smaller degree. 



When three dark-red nasturtiums were placed on yellow paper 2 inches 

 from the hole, 46 of 146 wasps noticed them by flying to them and almost 

 alighting during a period of 5 minutes, while 29 of 126 noticed them in 

 the next 5 minutes. With the substitution of California poppies of a yellow 

 color for the red nasturtiums, the number was much smaller, being but 

 5 per hundred for 10 minutes instead of 28 per hundred, the previous 

 rate. Replacing the dark-red flowers brought the rate again to 18 per 

 hundred. To eliminate the effect of perfume, 3 light yellow nasturtiums, 

 which matched the paper even more closely than the poppies, were em- 

 ployed; these received but 3 notices per hundred, proving that the dif- 

 ferences observed were due to color and not to odor. 



