FOOD PLANTS OF THE GIPSY MOTH IN" AMEBICA. 5 



ously throughout the feeding season. It required the services of five 

 assistants to attend properly to the feeding work and to record the 

 necessary data. In addition, two assistants were employed to collect 

 the food plants that were used in these experiments. Some of the 

 species could not be secured in Melrose, and in a number of cases con- 

 siderable travel was necessary in order to supply the foliage for the 

 tests. During the summer of 1914 an assistant provided with a 

 motorcycle was able to collect most of the foliage. 



About the same number of assistants was required to conduct the 

 experiments at the sublaboratory at Worcester, Mass., during the 

 summers of 1912 and 1913. 



A few tests or field observations were made on European trees and 

 shrubs which occur in New England, but no effort has been made in 

 this report to consider the food plants of the gipsy moth in Europe. 



DIFFICULTIES IN CONDUCTING THE EXPERIMENTS. 



As a result of previous experience in feeding caterpillars, it seemed 

 necessary to secure a better method than simply placing leaves or 

 twigs with foliage in the trays. When this is done the leaves wither 

 rapidly in warm weather and often become so dry that it is extremely 

 difficult to find all the first-stage caterpillars when the trays are 

 cleaned. The use of the bottles of water in the trays obviated this 

 trouble to a great extent and made the cleaning of the trays relatively 

 easy. There were several kinds of foliage, such as linden, sassafras, 

 and young growth of hickory, walnut, etc., that wilted rapidly in 

 spite of every precaution that was taken. 



In most of the trays a considerable number of caterpillars died 

 from the disease known as " wilt," and in a few cases the imported 

 parasites produced heavy mortality among the gipsy-moth larvae. 

 These factors operated in varying degrees during different seasons, 

 but had an important bearing on the number of larva? that survived 

 the tests. 



FOOD PLANTS TESTED. 1 



Note. — The writer expresses his appreciation to all who have assisted in these 

 experiments. Special thanks are due to the Board of Park Commissioners of 

 Worcester for the use of the sublaboratory in their city and to Mr. A. V. Parker, 

 superintendent of parks, and Mr. H. L. Neale, city forester, for many courtesies 

 extended; to Dr. C. S. Sargent and his assistants for permission to secure 

 foliage at the Arnold Arboretum for some of the experiments ; and to Mr. H. A. 

 Preston for preparing the photographs illustrating this report, as well as to 

 the many other einplos^ees of the Gipsy Moth Laboratory who have contributed 

 toward the data summarized in this report. 



1 The botanical designations, both scientific and common names, herein cited are verified 

 by Britton and Brown, Illustrated Flora of the Northern States and Canada. Second 

 Edition, Vols. I-III, New York, 1913. 



