6 Zoologia: N. Y. Zoological Society. [Vol. I 



M. Vernon, "observations as to the effect of moisture are ex- 

 ceedingly meagre. This is probably attributable to the fact 

 that in most cases a direct effect is either slight or wanting. 

 * * * In any case, the effect is probably an indirect one, acting 

 through the vegetation." 



In the summary of a series of thorough and very signifi- 

 cant experiments relating to the effects of temperature and moist- 

 ure on various species of the Coleopteran genus Leptinotarsa, 

 Prof. W. L. Tower draws the following conclusions which he 

 believes hold good for all insects. 



1 — The different factors of the environmental complex do 

 not have any specific influence upon coloration, but all act alike 

 as stimuli, either alone or in combinations, to accelerate or retard 

 color development, and thus to modify coloration in the following 

 ways: 



a — Toward melanic or albinic conditions, which are the 

 most general and important in coloration. 



b — Toward suppression or accentuation of particular color 

 areas or groups thereof. 



c — Toward changes in the colors themselves. 



2 — The factors most potent in the modification of coloration 

 are temperature and moisture; soil and altitude act indirectly 

 through moisture and temperature, while the influence of food, 

 light, and other factors is very slight. 



3 — Any factor acting as a stimulus produces at once the 

 maximum response which the deviation in the factor is capable 

 of producing, and this maximum response remains constant as 

 long as the stimulus is in force, but varies as the stimulus varies, 

 and is lost when the stimulus is removed. 



4 — Any factor which deviates either above or below the nor- 

 mal has the effect up to a certain point of producing increased 

 pigmentation, and beyond that point of retarding it. 



5 — Variations produced by the action of environmental fac- 

 tors during ontogeny always follow the laws of fluctuating varia- 

 tions. New combinations of color characters never appear as 

 the result of stimuli applied during ontogeny, and the modifica- 

 tions found are all in the line of accentuation or reduction of 

 the color characters natural to the species. 



6 — The variations produced in experiment resemble in their 

 polygons of distribution and in their modal classes conditions 

 found in nature in places or in seasons in which the conditions 

 of existence are similar to those of the experiment ; and a varia- 

 tion found in nature is to be interpreted as the result of a devi- 



