FOOD PLANTS OF THE GIPSY MOTH "IN AMERICA. 9 



The tray experiments were not satisfactory because of the difficulty of secur- 

 ing a satisfactory food supply, but all the larvae grew well in the early stages. 

 Red birch is a favored food plant. 



Yellow Birch (Betula lutea Michx. f.). 



Except in heavy infestations, most of the feeding on this species by gipsy- 

 moth larvae is done in the first three stages. The larva? make small holes, 

 extending entirely through the leaves, forming " pinholes," and a few days 

 later " shot holes." If the infestation is bad and the associated species of food 

 plants are defoliated, these birches are sometimes stripped. 



In tray experiments male moths have been secured by feeding larva? started 

 in the first stage. 



High Blackberry (Rubus sp.). 



Field observations indicate considerable variation in feeding on this plant. 

 Defoliation has seldom been reported, and then only when heavy infestations 

 occurred. Under ordinary conditions the feeding on this species is very slight. 



Low Blueberry (Vaccinium vacillans Kalm.). 



Of the three species of Vaccinium under observation in this series of experi- 

 ments, this is the most unfavorable. Larva? in the field have been found 

 feeding in all stages, but not to any extent, except in medium to grossly 

 infested territory. Usually the last three stages do most of the feeding on 

 these shrubs. 



First-stage caterpillars fed in trays have produced moths, which indicated 

 that the insect can survive on this species. 



Tall Blueberry (Vaccinium corymbosttm L.). 



All the field observers consider V. corymbosum more susceptible to gipsy- 

 moth attack than V. vacillans, but it is not favored when other food is avail- 

 able. When an infestation is fairly heavy it is- not uncommon for these shrubs 

 to be entirely denuded. 



First-stage caterpillars have developed to the adult stage when fed in trays. 

 The larvse did not grow as rapidly as is normal and were undersize. 



Blueberry (Vaccinium angiistifolium Ait.). 



The field observers pronounce this species the most susceptible to moth 

 attack of our three common species. They note feeding in the early as well as 

 the late stages, and the shrubs may be found in all stages of defoliation. 

 When a tree has been completely defoliated by the larva? and they migrate to 

 another tree, these shrubs furnish food for the journey. 



First-stage larva? fed in trays grew rapidly and large vigorous adults 

 resulted. 



-Box Elder (Acer negundo L.). 



No field observations are recorded on this species. 



Tray experiments indicate that this is one of the most susceptible of the 

 maples to moth attack. The larva? fed freely in all stages and grew to large 

 size ; specimens started in the first stage produced moths. 



92719°— 15 2 



