THE CANADIAN EXTOMOLOGIST. 147 



another, and the varieties may be found feeding on the same tree. How, 

 then, can the food have anything to do with the variation ? Eadcs 

 i?}ipe?'ialls is single brooded with us, but still the larva is found in August 

 as well as in October, and no difference in color is observable at one time 

 more than another. In a previous number I related an experiment made 

 with a brood of imperialism and, in that case, every one of the larvae were 

 dark. 



The chemistry of biology is doubtless a very abstruse subject, but it is 

 well worth any labor that niay be bestowed on its investigation. The 

 larva of A. luua feeding, say, on Sweet Gum, produces an insect of a 

 beautiful green color. That of Each-s imperiaHs, feeding on the same 

 food, produces an insect of which yellow and purple are the predominant 

 colors, while that ot rcgalis produces an imago yellow and red. Here are 

 larvae all similarly constituted as regards masticatory and digestive 

 powers^ and the substance acted upon is the same in each case, and yet 

 how different is the result. This is very wonderful. What is there in the 

 constitution of the digestive organs of these respective larvae that enables 

 one to eliminate this color, and another that ? Of course similar results 

 may be observed in other animals, and the same beefsteak may contribute 

 to the growth of a negro as well as of a white man, but still this does not 

 diminish the difficulty we have in understanding how it is done. Ento- 

 mology is a fascinating pursuit, looked at as merely an amusement, but I 

 have an a]>iding faith that it is destined to throw more light on the 

 phenomena of life than perhaps any other branch of science can. But 

 we must avoid hasty conclusions. 



I have selected only one instance from Mr. Gentry's paper, but there 

 are others. For example, the same objections may be made in the case 

 of Sphinx ^-inaadata as are made in that of imperialis. The different 

 colors appear at the same season, and may be found feeding on the same 

 tomato plant. 



ON THE LARVA OF CATOCALA ULTROXL\, Huen. 



BY THE EDITOR. 



For several years past, while jarring our plum trees for Curculio in 

 June, we have taken the larva of a Catocala usually less than half grown, 

 but have never succeeded in rearing any of them until this season, when 



