THE BIOLOGY OF LIGHT PRODUCTION IN ARTHROPODS 



By N. S. Rustum Maltjf 

 The Osborn Zoological Laboratory, Yale University 



* * * all the fire emitted by wood and other combustibles when burning, existed in 

 them before in a solid state, being only discovered when separating — 



— Benjamin Franklin 



Luminescence, in contrast to incandescence, is the emission of light 

 as a result of some other factor than heat. There are various types 

 of luminescence: (1) Thermoluminescence is the emission of light at 

 abnormally high temperatures but nevertheless at temperatures well 

 below 525° C. It resembles phosphorescence in that it is dependent 

 on previous irradiation, e. g., fluorite will cease to emit light at 100° C. 

 if kept in the dark for a long time. Since not all phosphorescent sub- 

 stances are thermoluminescent, thermoluminescence is probably not 

 merely a case of phosphorescence intensified by heat. (2) Phos- 

 phorescence and fluorescence are the emission of light as the result of 

 an absorption of radiant energy. In fluorescence the emission (gen- 

 erally of a longer wave length than the incident light) occurs only 

 during the time of irradiation. Harvey (1919) has pointed out, 

 however, that the distinction between fluorescence and phosphores- 

 cence is probably only arbitrary since some substances will yield light 

 for only 1 /5,000 of a second after irradiation and since some substances, 

 which fluoresce at ordinary temperatures, will phosphoresce at low 

 temperatures. Chitin, eosin, and most proteins will fluoresce in 

 ultraviolet light so that an excursion of a human being into an imagin- 

 ary world in which there is no incident visible light but in which there 

 is ultraviolet irradiation would not mean that all would be darkness. 

 He would be able to see living organisms and various minerals. (3) 

 Triboluminescence results from the shaking or rubbing of certain 

 crystals, e. g., uranium nitrate, sucrose. (4) Crystalloluminescence is 

 observable when certain substances in solution are crystallizing out, 

 e. g., AsO, NaF. All such substances are triboluminescent but the 

 converse is not true. It has been shown that crystalloluminescence is 

 not necessarily due to friction. (5) Chemiluminescence, in contrast 

 to the above types of luminescence, is an oxidation and generally, if 

 not always, requires oxygen or ozone. It thus includes the lumines- 



i Reprinted by permission from Science Progress, vol. 32, No. 126, October 1937, with extensive revisions 

 and additions by the author. 



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