1864.] 403 



ON PHYTOPHAGIC VARIETIES AND PHYTOPHAGIC SPECIES. 

 BY BENJ. D. WALSH, M. A. 



It is well known, especially to breeders of Lepidoptera, that there 

 are certain species of Insects, which in the larva state feed only on one 

 particular species or a few closely allied species of plants, and others 

 which feed on a great variety of plants belonging to difterent species 

 and genera, and even to diiferent and widely distinct fiimilies. For 

 example, Attactis Luna Drury occurs only on the walnut and hickory, 

 while Attacus Gecropia Lin. is found, according to Harris, on apple, 

 cherry and plum trees, and on currant and barberry bushes, and I have 

 reason to believe that it feeds also on the common hazel. But there is 

 a still more remarkable example of diversified tastes in Dri/ocampa 

 hnperialis Drury, which feeds sometimes on the sycamore, an angio- 

 spermous tree, and sometimes on the pine, a gymnospermous tree. 



Occasionally this difl'erence of food causes certain differences in the 

 insect itself, either in the larva or in the imago state. Thus the larvas 

 of Datanu mlniatra Drury that occur on the oak, the apple tree, the 

 thorn and several other trees, almost invariably have a large yellow 

 spot behind the head, and always have pale longitudinal lines on the 

 body ; while those that are found on the hickory are either entirely 

 black, or are longitudinally lineate with whitish without any yellow spot 

 behind the head. But as this last variety also occurs on the oak, and 

 the imago bred from the black variety on the hickory is absolutely 

 identical with the imago bred from the yellow-necked and striped va- 

 riety on the oak, as I have experimentally ascertained, it would seem 

 that the two forms cannot be distinct. Again, I have taken numerous 

 specimens of Chrysomela scalaris Lee. on the elm and basswood, which 

 measure in length .35 — .40 inch ; and on the dogwood (cornus) and 

 wild plum I have for many years back taken whole swarms along 

 with their larvje, which ranged from .27 to .30 inch in length, and 

 none of which exceeded the latter measurement. Yet on the closest 

 inspection I could discover no other distinctive character but size, and 

 on forwarding specimens of both forms three years ago to Dr. LeConte 

 with a statement of the facts, they were pronounced by him to be iden- 



