tions as Leguminosa? with Pinaceae, or with Rhamnaceae, 

 Polygonaceae, Cupuliferae in the case of different larva?. 

 More uniformity should certainly be expected if the se- 

 lection of diverse plants depended upon the actual chem- 

 ical characteristics of the plant tissue. We should have 

 also to assume that the digestive functions of the cecropia 

 caterpillar with its sixty-odd food-plants were funda- 

 mentally different from those of monophagous caterpil- 

 lars. 



There is much in the behavior of certain species to 

 suggest that food-plants are selected on the basis of odor 

 by the parent female and also accepted on the same basis 

 by the larva?. Experiments with cabbage butterflies by 

 Verschaffelt and others show that these insects are at- 

 tracted by the mustard oils present in these plants, and 

 it has also been shown that caterpillars will feed on other 

 plants which have been treated with one of these oils. 

 Similar behavior in the most diverse insects is also known 

 in the attraction exercised by specific fermentation prod- 

 ucts {e.g., to Stomoxys, Drosphila, etc.). The distaste of 

 mosquitoes for oil of Citronella is well known, as is also 

 the attractiveness of this same substance for fruit-flies 

 of the genus Dacus. That the same cabbage butterflies 

 have definite dislikes in the way of plant odors has re- 

 cently been claimed by the Russian entomologist Schrei- 

 ber, who found that Pieris brassier would not attack cab- 

 bages planted in close proximity to tomatoes. Pieris 

 rapce does not seem to behave similarly, however, and this 

 dislike is probably not general among the crucifer-eating 

 Pierids. 



Very recently Mclndoo has published some observa- 

 tions showing that caterpillars readily react to the odors 

 of several essential oils and to those of various plants. 

 This, taken together with the fact that Pieris will feed 

 upon strange plants treated with mustard oil, would sug- 

 gest that odor is an important factor in the selection of 

 food-plants. Queerly enough, however, he found that the 

 response to their own food-plants was no more rapid 

 than to the other substances, and even slower in some 



