2OO ENTOMOLOGY 



Pictet has recently found, however, that humidity acting 

 on the caterpillars of Vanessa urtica? and V. polychloros has 

 a conspicuous effect on the coloration of the butterflies. Thus 

 when the caterpillars were fed for ten days with moist leaves, 

 the resulting butterflies had abnormal black markings on the 

 wings, and the same results followed when the larvae were 

 kept in an atmosphere saturated with moisture. 



Climatal Coloration. The brilliant and varied colors of 

 tropical insects are popularly ascribed to intense heat, light 

 and moisture ; and the dull monotonous colors of arctic insects, 

 similarly, to the surrounding climatal conditions. Climate 

 undoubtedly exerts a strong influence upon coloration, but the 

 precise nature of this ;nfluence is obscure and will remain so 

 until more is known about the effects separately produced by 

 each of the several factors that go to make up what is called 

 climate. 



The prevalence of intense and varied colors among tropical 

 insects is doubtless somewhat exaggerated, for the reason that 

 the highly colored species naturally attract the eye to the ex- 

 clusion of the less conspicuous forms. Indeed, Wallace 

 assures us that, although tropical insects present some of the 

 most gorgeous colors in the whole realm of nature, there are 

 thousands of tropical species that are as dull colored as any 

 of the temperate regions. Carabidae, in fact, attain their 

 greatest brilliancy in the temperate zone, according to Wal- 

 lace, though butterflies certainly show a larger proportion of 

 vivid and varied colors in the tropics. Mayer finds, in the 

 widely distributed genus Papilio, that 200 South American 

 species display but 36 colors, while 22 North American species 

 show 17. While the number of species in South America is 

 nine times as great as in North America, the number of colors 

 displayed is only a little more than twice as great; hence 

 Mayer concludes that the richer display of colors in the tropics 

 may be due to the far greater number of species, which gives 

 a better opportunity for color sports to arise; and not to any 

 direct influence of the climate. Furthermore, the number of 



