424 PACKARD— ORIGIN OF MARKINGS OF ORGANISMS. [Dec. 2, 



We fall back on the experiments of Steinach, which demonstrate 

 that light often acts as a direct stimulus. He glued strij^s of black 

 paper to the skin of frogs which were kept in the dark ; when they 

 were exposed to the light only the uncovered parts of their skin 

 returned to a lighter color, while the covered parts remained dark. 

 To avoid all doubts the experiments were repeated on skin sepa- 

 rated from the body, and photograms of letters and flowers, cut out 

 of black paper and glued to the skin, were reproduced upon it. 

 These experiments prove the truth of Biederman's claim that 

 the color-cells of the frog change their shape owing to the direct 

 action of light and temperature.^ 



The researches of Krukenberg and others show that light has a 

 marked influence on the colors of insects; and the criticisms of 

 Hagen, with the later researches of Hopkins, Urech, Mayer and 

 others on pigments, all tend to show that the colors and markings 

 of insects and other animals which by some theorists are attributed 

 to natural selection, are really the result of the action of the 

 primary factors of evolution, such as changes of light, heat and 

 cold, moisture and dryness, etc., color and pattern being at the 

 outset produced by metabolic and physiological processes.'"^ 



So-called warning colors in Coleoplera, etc. — Some of the so- 

 called '^ warning patterns " of ground and tiger beetles, especially 

 the former (Anthia), are claimed by Marshall and Poulton to be 

 *' very remarkable and effective." They are ornamented with 

 large spot and stripes. When alarmed they are said to adopt a 

 very characteristic warning attitude, and like Brachinus they eject 

 to the distance of from four to five feet a strong acid secretion 

 which produces a strong stinging sensation when it touches the skin 

 of the face or back of the hands. 



Here it should be observed that these spotted Carabidae, unlike 

 the majority of the family, are diurnal in their habits, preferring 

 open, treeless places exposed to the direct heat and sunlight. 



They are purely terrestrial in their habits, very conspicuous, and 

 prefer an open, treeless country; they can project an acid, caustic 

 secretion to a distance of four or five feet. 



Upon looking over the beautiful plates illustrating Marshall and 

 Poulton's interesting memoir, it strikes one that in accumulating so 

 many examples of warning colors, they attempt to prove too much. 



1 Pfliiger's Archiv F/iys., p. 51, 1892. 



2 See our Text-book of Entomology^ pp. 201-210, for abstracts. 



