REACTIONS OF LARV/E TO LIGHT. 26" 



Monochromatic light was secured by means of Wratten 

 Light Filters Nos. 70, 71, 72, 74, 75, 76, and a combination filter 

 composed of Nos. 22 and 53 made by Eastman Kodak Company. 

 Each filter transmits a rather narrow band of the visible spec- 

 trum, most of the light being limited to a band 40 ^ wide or 

 less. The per cent, of incident light of various wave-lengths 

 transmitted by these filters has been measured by Eastman 

 Kodak Company and is represented graphically by the white 

 areas in Fig. 2. 



The distribution of energy in the spectrum of the 15-watt 

 Mazda lamp used in connection with the filters was ascertained 

 by the U. S. Bureau of Standards (Fig. 3). 



Since the distribution of the energy incident on the filters 

 (Fig. 3) and the portion of this energy transmitted by each 

 (Fig. 2) was known, and both had been ascertained for bands 

 10 up wide, it was possible to compute the relation in the energy 

 of the light transmitted by the different filters in conjunction 

 with the lamp in 10 ^ bands (Table I.). 



TABLE I. 



4 



RELATIVE ENERGY TRANSMITTED BY DIFFERENT WRATTEN LIGHT 

 FILTERS WITH IS-WATT MAZDA LAMP. 



Filter Number. Relative Energy. 



70 (red) 1 1 76.0 



71 (red) 225.0 



72 (orange) 74.0 



22 and 53 (yellow) 38.5 



74 (green) 39.3 



75 (green) 51.8 



76 (blue) 10.35 



In addition to the transmission in the visible spectrum all the 

 filters transmit infra-red, but these rays were found to be ineffec- 

 tive for the larvae of both Palcemonetes vulgaris and Loligo pealii. 

 This was determined by subjecting them to light from which 

 nearly all the visible rays were removed by means of Wratten 

 Light Filter No. 88 which transmits only rays beyond 700 MM- 

 Since the infra-red rays proved to be ineffective in stimulating the 

 \arvse, they may be left out of consideration. 



Ultra-violet was screened out by several layers of glass through 

 which the light passed. 



