REVIEW OF LITERATURE 



Literature is voluminous on the subject of the effectiveness of various wavelengths 

 of radiation for stimulating responses 5 in insects. Spectral response curves have been 

 determined for a wide variety of adult and larval forms of insects and the region from 

 253.7 mjx to 700 m^i has been shown to contain those wavelengths most effective in pro- 

 ducing responses. In general, three different techniques have been employed in deter- 

 mining these curves (17). These techniques include (1) training, individual responses, or 

 field observations, (2) the use of electroretinograms (ERG), and (3) studies of group 

 motor responses to radiant energy. Work on response determinations will be considered 

 in order under these three general classifications. 



Field Observations, Training, and Individual Response Studies : Probably because of lack 

 of suitable energy sources, highly refined optical equipment and sensitive radiometry 

 equipment (or failure to realize the importance of wavelength) most of the early work on 

 spectral response determinations of insects was confined to observations of natural 

 phototropic effects or to experiments involving training of individual insects. Weiss (22) 

 points out that these early investigators apparently paid little attention to wavelength 

 aspects of the problem, and interpreted the behavior of the insects in terms of human 

 color vision. He reviews this early work thoroughly and reports: "Sir John Lubbock 

 established the fact that bees were apparently able to distinguish one color from another 

 and could be trained to associate the finding of food with blue or orange colored papers. 

 Auguste Forel accomplished the same thing with colored paper flowers. C. Hess projected 

 a spectrum on a parallel- sided glass container that held imprisoned insects and observed 

 that caterpillars and adults of the butterfly Vanessa urticae , and also bees, went to the 

 yellow-green area. From these observations, Hess concluded that since totally color- 

 blind persons see yellow-green as the brightest part of the spectrum, his insects were 

 also totally color-blind. . . . K. Frisch trained an Asiatic species of honeybee to come 

 to a given color for food and to pick out that color from among others when no food was 

 present. . . . After conditioning the bees to various colors, Frisch concluded that bees 

 could distinguish all colors except red and certain greens and that these colors appeared 

 to them as darker or lighter grays, and that, therefore, their color vision was identical 

 with that of partially color-blind persons. . . . Frank E. Lutz tested the colored papers 

 used by Frisch and found that some of his greens and blues reflected ultraviolet, that 

 his yellows and greens reflected blue and red, all of which invalidated Frisch's color 

 scale for insects. ... A. Kuhn and R. Pohl trained honeybees to come for food in a 

 narrow trough illuminated by ultraviolet of wavelength 3650 A. After training, the food 

 was removed and the entire spectrum was projected upon a sheet of white paper. Then 

 the bees collected for the most part on the place subjected to wavelength 3650 A. Frank 

 E. Lutz trained bees to come for food to a white card, reflecting ultraviolet wavelengths, 

 and stingless bees to distinguish between ultraviolet patterns. . . . L. M. Bertholf, in 

 an extensive study of the reactions of the honeybee to the spectrum visible to us, found 

 that for this insect the spectrum extended from 4310 A., to at least 6770 A., the point of 

 maximal stimulative effect being at about 5530 A. . . . He also worked with different 

 wavelengths in the ultraviolet spectrum and found that the stimulating effect was greatest 

 at 3650 A. for the honeybee." 



Electroretinogram (ERG) Studies : The ERG is obtained by connecting electrodes near 

 or directly to the optic nerves or by the use of contained electrolytes in contact with the 

 surface of the eye into which electrodes can be inserted for picking up the induced poten- 

 tials. The potentials developed when the eyes are subjected to intermittent or continuous 

 radiation are transmitted to high gain electronic amplifiers and subsequently appear as 

 traces on a recording oscilloscope or similar recording device. The curve or trace 

 resulting from the external stimulations is called the electroretinogram. According to 

 Jahn (12) spectral sensitivity curves can be obtained from the ERG by relating the 

 magnitude of potential of any component of the ERG to the wavelength of incident radiation. 



5 See definition of response, footnote 2. 



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