Many different light sources have been utilized in observing insect attraction to 

 light. An open fire was probably the first, followed by the candle, kerosene lamp and 

 lantern, acetylene lamp, gasoline lantern, carbon-filament electric lamp, and finally by 

 the electric lamps utilized today. These include the incandescent using a tungsten- 

 filament, and various gaseous discharge sources employing mercury and other gases 

 and vapors such as argon, neon, and xenon. The fluorescent lamp is a mercury vapor 

 discharge source. 



Light from a fire, the candle, the kerosene lamp, and the lantern is a weak yellow. 

 That from the first incandescent electric lamp, equipped with carbon filament, is also 

 yellow but of greater intensity. Certain gasoline lanterns and the acetylene lamp provide 

 white light with much less yellow and considerably more blue and violet. Likewise, the 

 tungsten-filament lamp provides white light and, with special glass bulb, a limited amount 

 of ultraviolet. The mercury and argon gaseous discharge lamps have been the most com- 

 mon sources of ultraviolet light used in our recent studies on insect attraction. 



Incandescent, fluorescent, and certain other gaseous discharge sources are being 

 used at the present time in insect survey traps in the United States. 



The incandescent lamp, with its tungsten filament, is usually filled with an atmos- 

 phere of argon and nitrogen to retard evaporation of the filament. Relative energy 

 radiated in the visible region is lowest in violet blue and highest in the red regardless 

 of filament temperature. The major portion of the energy input to the lamp, 75 to 85 

 percent, is radiated in the infrared region. As previously indicated, limited ultraviolet 

 is radiated with special glass bulbs. 



The fluorescent lamp is a mercury vapor discharge source acting on light-generating 

 phosphors. The lamp generates ultraviolet radiation at a wavelength of 2537 A. Phosphors, 

 which are powders or chemicals, coat the inside of fluorescent lamps and transform 2537 

 radiation into longer wavelengths. A very low mercury vapor pressure, roughly one, one 

 hundred-thousandth of normal atmospheric pressure is held in the tube. 



The BL (black light) lamp is an example of converting 2537 radiation into longer 

 wavelength ultraviolet radiation. The curve of the relative spectral emission of this 

 lamp is shown because of the radiation in the green as well as in the near ultraviolet. 

 The BLB lamp varies from the BL lamp only in that it is self-filtered with a red-purple 

 bulb. This bulb absorbs the visible light radiated by the BL lamp. Other phosphors con- 

 vert 2537 radiation into visible light of various wavelengths. 



Mercury lamps other than the BL and BLB fluorescent have been used in insect 

 attraction studies, because all mercury lamps supply radiation in the black-light region. 

 Spectral output data are available on the various types and sizes in tabular form to serve 

 as a guide in selecting the lamp with greatest radiation at the wavelength desired. Two 

 lamps, the H100A4 and H400E1, are of particularly high near ultraviolet output and both 

 have been used rather extensively in field insect attraction studies. The radiant power 

 of the H400E1 is greatest in the near ultraviolet but is also large in violet, blue, green, 

 and yellow. 



Another lamp, the argon glow lamp, has been of considerable value in attracting 

 the pink bollworm moth. This lamp, which consists of a mixture of gases, radiates mainly 

 blue, violet, and in the near ultraviolet region. The spectral emission curve for this lamp 

 indicates the predominance of its radiation in the near ultraviolet region. Radiation by 

 the neon glow lamp on the other hand is in the yellow, orange, and red. 



Mention should be made of the infrared radiation from a female Cecropia moth 

 measured and published by Duane and Tyler in 1950. Quoting directly they report "ap- 

 parently she radiated in a definite pattern in the region from 3 to 1 1 microns." This is 

 in the infrared region and equivalent to 30,000 to 110,000 A. An answer to the authors' 

 question "Is this radiation the attracting medium which guides the male moth through fog 

 and darkness to his mate?" has not yet been given as far as can be determined. 



