30 Experimental Zoology 



name implies) and on the leaves of certain shrubs. It is now 

 found on a number of other trees. 



' Certain aberrations have been traced directly to the food of 

 the caterpillar. The caterpillars of Ellopia prosapiaria living 

 on the pine become reddish butterflies; but if they occur on 

 the fir, they give rise to the aberration prasinaria, which is 

 green. An analogous case is that of Cidaria variata, whose 

 caterpillars living on the fir give rise to a form that is gray, but 

 on the pine produce a variety obeliscata, which is brownish red. 



In certain countries where a variety almost entirely replaces 

 the parent species it is not uncommon to find the caterpillar on 

 a different plant. For example, Lasiocampa quercus lives on 

 different food plants in different countries. In Scotland, where 

 the variety callunae dominates, the caterpillars live on the 

 heather; in the South, where the variety roboris is found, the 

 caterpillars live on the oak, Quercus robur. 



In changing the food, Pictet often made use of plants that 

 were very different from the natural one. Thus the oak was 

 often replaced by the esparcette, 1 by the dandelion, by the 

 lettuce or by the pimprenelle. 2 In other cases it was replaced 

 by the walnut, neflier, 3 and the sorbier. 4 In some cases a food 

 plant closely related to the normal was the only one that could 

 be substituted ; thus the European Evonymus europaeus (spindle 

 tree) can be replaced by E. japonicus. Certain species refuse 

 all food but their natural one. Other species can be induced 

 to take a different nourishment, but only after much persever- 

 ance. Others, such as Lasiocampa quercus, when young ac- 

 commodate themselves to nearly all kinds of vegetation, but 

 once full size, many plants are rejected. The acceptation of a 

 new kind of food is transmitted by heredity, and individuals 

 whose parents have become accustomed to a strange food will 

 consume the same food with greater facility. Some of the 

 effects that Pictet obtained by changes in the food are as fol- 

 lows : 



1 Onobrychis sativa, or holy clover. 3 Mespilus germanica, or mespit. 



2 Poterium sanguisorba, or salad burnet. 4 Sorbus ancuparia. 



