New York Agricultural Experiment Station. 399 



of seeming morphological and biologic differences the separation 

 of these insects is difficult and unsatisfactory, and there exists 

 consequently considerable uncertainty as to the actual status of 

 these two forms. 



According to Dr. Marchal ^ " the ground color of the front wings 

 is entirely white with malineUus, and more or less tinted with grey 

 with padellus. The fringe of the anterior wings, examined from 

 below, is whitish for the most part with malineUus, while with 

 padellus it is grey or almost entirely grey. Finally the under- 

 surfaces of the front wings of padellus are entirely grey, while the 

 margins of the wings of malineUus, examined from below, are finely 

 bordered with white padellus is extremely vari- 

 able, and the variation extends to the characters which are used 

 to distinguish it from malineUus. Certain examples have the 

 anterior wings largely tinted with grey, others have white wings, 

 while some are intermediate. The fringes are also variable in their 

 coloration, and the narrow white border of the lower surface is not 

 always a constant character." 



Some apparent differences in feeding habits and appearances 

 of the caterpillars, and in the coloration of the pupas and texture 

 of the cocoons have also been noted. Lewis ^ in 1836 called atten- 

 tion to the fact that the larvfB of the Yponomeuta on apple upon 

 emerging from the egg masses in the spring are leaf miners. This 

 was verified by Delacour ^ in 1850 and Bissiere ^ in 1876 and while 

 this habit has been overlooked by many writers it has been described 

 with much detpil by Mokshetsky in his recent treatise. Marchal 

 also records that mahalebellus,^ a closely related species, similarly 

 burrows into the leaves of the Mahaleb cherry. Curiously enough 

 the mining instinct which manifests itself with the foregoing species 

 has apparently not been observed or at least satisfactorily estab- 

 lished for padellus caterpillars. Rebate and Bernes also call atten- 

 tion to apparent preferences for host plants which, coupled with 

 slight differences in the appearance of the moths, larvge and pupse 

 are given by them to support the opinion that the insects represent 

 distinct species. According to them branches of plums and apples 

 may intercross, and, depending on which of the two forms is present 

 one fruit will have the foliage eaten while the other will be immune. 

 Moreover in some experiments conducted by them the larvse of 

 padellus, reared on plum, would not attack apple foliage; and vice 

 versa caterpillars of malineUus taken from apple would not feed on 

 plum. To the contrary Gruvel ^ states that in a test conducted 



1 Bui. Soc. d'Etud. et Vidg. Zool. Agric. p. 23, 1902. 



2 Trans. Ent. Soc. London 1 :21-22, 1836. 

 ' Essai siir les Insectes, 1850, p. 296. 



^ Bill, d' Insectologie Agricole, No. 4, p. 83, 1876. 



6 Bui. Soc. d'Etud. Vulg. Zool. Agric, p. 21, 1902. 



' Quoted from La Chenille Fileuse, Rebate and Bemes. 



