REACTIONS OF ARTHROPODS TO LIGHTS 495 



greatest directive stimulus on Drosophila. The effectiveness of 

 the colors beginning with the strongest is, therefore, in the fol- 

 lowing order: blue, green, yellow, red. 



D. Zeuzera pyrina Linne (larva) 



The lepidopterous insects are, as far as I know, unlike the 

 dipterous in that there is no reversal of their phototropism during 

 development. Both the caterpillars and the adults of the species 

 of moths and butterflies^ known to be responsive to directive 

 hght are distinctly positively phototrophic. 



1. Material. The larva of the European wood leopard-moth, 

 Zeuzera pjTina Linne, used in these experiments, was accidently 

 introduced into this country from Europe, and has since proven 

 to be a serious pest to our shade trees and shubbbery. This 

 species of moth has not, to my knowledge, ever been the sub- 

 ject of hght experiments, but Chapman ('11, p. 15) states: 

 "The larvae when they first hatch exhibit a marked positive 

 phototaxis for they make their way to the tips of small branches 

 to the axis of leaves or to nodes and buds near the tips, and at 

 once bore into the woody tissue." 



This suggests an interesting correlation of the positive photo- 

 tropism of these insects with their habits during the early stage 

 of their life history. 



Unlike the blow-fly larvae the leopard-moth larvae are most 

 responsive during the early part of their free hfe. They become 

 more and more sluggish in their reactions to light as thej^ approach 

 the pupal stage which, according to Chapman, is not attained 

 until the second year. 



The larvae were abundant in the twigs and branches of many 

 of the trees and shrubs, especially the lilacs in the "\dcinity of 

 the Museum of Comparative Zoology, Cambridge. The lilacs 

 provided an abundant and convenient source of material. A 

 considerable number of the larvae used in these experiments 

 were secured by Mr. Chapman from the trees and shrubbery 

 of Boston Common. Since the larvae are somewhat troublesome 



1 The reactions of Venessa antiopa Linn, is an apparent exception. These 

 butterflies when alighted turn away from bright sunlight. Parker ('03). 



