RELATION OF WAVELENGTH TO INSECT RESPONSE 



Joe P. Hollings worth 



INTRODUCTION 



The purpose of this report is to present a review of previous work on the relation of 

 ■wavelength of electromagnetic radiation to insect response 2 and to relate these results 

 to recent findings by the Farm Electrification Research Branch Laboratory at College 

 Station, Tex., on response characteristics of the pink bollworm moth ( Pectinophora 

 gossypiella (Saund.)). 



THE ELECTROMAGNETIC SPECTRUM 



The nature of all electromagnetic radiation in the spectral region under consideration 

 (2,000 to 10,000,000 Angstrom units 3 ) is the same in that the principles governing this 

 radiation are based on the laws (1) that a moving electric field creates a magnetic field 

 and (2) that a moving magnetic field creates an electric field. The created field at any 

 instant is always in phase in time with its parent field, but is perpendicular to it in 

 space (15). 4 The velocity or speed of this radiation when transmitted through space is 

 that of light, or about 186,000 miles per second (3 x 10* cm. /sec.) and the various 

 radiations differ only in frequency and wavelength. Since Velocity (a constant) = Fre- 

 quency x Wavelength, then wavelength is an inverse function of frequency, i.e., as the 

 frequency is increased, the wavelength decreases and vice versa. The study and under- 

 standing of the various regions of the entire electromagnetic spectrum are greatly 

 simplified if one remembers that the entire wavelength scale represents the same type 

 of radiant energy throughout and differs only in wavelength. 



Light is defined as electromagnetic radiation to which the human organs of sight 

 react and is generally considered to include the region between 390 and 770 m/i. Luckiesh 

 (14) has defined various spectral ranges by names now commonly used as follows: 



Millimicron 



Middle ultraviolet 200 to 300 



Near ultraviolet 300 to 390 



Violet 390 to 430 



Blue 430 to 490 



Green 490 to 550 



Yellow 550 to 590 



Orange 590 to 620 



Red 620 to 770 



Infrared 770 to 10 x 10 5 



In general, the effect of radiation is directly proportional to its absorption, -with 

 chemical effects being of primary importance in the region below 390 mfi, and visual 

 effects which allow discrimination of color and detail predominate in the region from 

 3 90 to 770 m/i. Heating effects are associated with wavelengths longer than 770 mjj (the 

 infrared region) although all forms of radiant energy are eventually dissipated as heat. 



1 Agricultural Engineer, Farm Electrification Research Branch, Agricultural Research Service, U.S.D.A., College Station, Tex. 



2 "Response" as used in this report will refer to the measurable or observable reactions of insects when the insect is subject to 

 irradiation by electromagnetic radiation. 



3 10 Angstrom units = 10" 7 cm. = 1 millimicron (m/i); therefore, the region of electromagnetic spectrum under consideration 

 covers from 200 to 1,000,000 m/i. The latter nomenclature will be followed throughout this paper. 

 4 Figure numbers in parentheses refer to Literature Cited at end of this paper. 



