THE CAXAUIAN ENTOMOLOGIST. 89 



the body, their outline being indicated by the prominence due to their 

 beaded structure. Spiracles dark^ with no trace of light annuli. Observed 

 during the middle ot October, in the vicinity of Bristol, Penn., feeding 

 >upon the frost-bitten leaves of Nicotiana tabacum. 



CONCLUSIONS. 



That the abnormal forms described above should present such curious 

 'deviations from the ordinary normal type, is to me a rather interesting 

 occurrence. That they are to be considered as the effects of a legitimate 

 cause is a settled conviction in my mind. What the cause is it will be 

 my aim to show. Happening at a period when the leaves of plants show 

 a diminished state of vitality, and are assuming the characteristic hues of 

 the season in consequence of the introduction of chemical changes into 

 their parenchymatous material, it seems that the variations are in some 

 way connected with defective ?iutritioit. The unusually small sizes of the 

 larvae, when compared with the normal forms, add great weight to such 

 an opinion. 



It will be seen that the colors of the caterpillars rival those of the 

 changing leaves. In few cases all the transitional color stages from the 

 natural one of the larva to that which is last assumed, were distinctly 

 observed by the writer, thus clearly proving the two facts to be connected 

 -^vith each other in the relation of effect and cause. 



If the beautiful and varied shades of green which many caterpillars 

 present can be attributed to the green and granular chlorophyl of the 

 leaves upon which they subsist, the conclusion must be irresistible that 

 when chemical or other changes are inaugurated in the parenchyma of the 

 leaf, thereby inducing color changes, the introduction of such food into 

 the insect's economy must giA'e rise to changes therein which will have a 

 tendency to vary its external coloration and markings. 



'Tis true that the variable colors of animals in many cases are 

 brought about through the intluence of the 7c////. The changeableness of 

 our ordinary Hyla versicolor, Lee, might be cited as an example, and the 

 number of such might be prolonged to considerable length, but the 

 cases are so numerous and so well known that it would not be advisable 

 to give them notice in a paper like the present. In the above example 

 the color variableness serves to conceal the animal from its enemies by 

 adapting it to the colors of objects upon which it chances to place itself. 



