DISPERSION OF GIPSY-MOTH LAKV^ BY THE WIND. 17 



isolated infestations are scattered in hill and dale over 19,378 square 

 miles of the New England States (PI. VII), excepting Vermont, 1 and 

 a comparison of such information with the foregoing data at once 

 suggests the source of practically all spread of this species. 



OBSERVATIONS ON WIND DISPERSION AT SALISBURY BEACH, MASS., 



IN 1913 AND 1914. 



Salisbury Beach, owing to its separation by extensive marshes from 

 infested woodlands and to the limited amount of favorable food plants 

 for gipsy moths thereon, was selected as a desirable location to be 

 cleaned up and watched for reinfestation. The south end of the 

 beach (PI. II), If miles in length, was scouted and the egg clusters 

 were creosoted in 1913 and 1914. Beach plum was the predominant 

 shrub growing on the sands and was not fed upon by the caterpillars. 

 Bayberry, wild rose, willow sprouts, balsam poplar, and other small 

 growth thrived to a certain extent and are favored food plants. 



The scouting in 1913 resulted in the finding of 144 egg clusters 

 distributed over the beach in a few clumps of shrubbery. The con- 

 trol work was followed up during the summer by frequent examina- 

 tions for caterpillars, which resulted in their discovery in seven or 

 more places other than where egg clusters were located. From 

 one to six caterpillars were found in small isolated clumps of bay- 

 berry and wild rose in no less than six spots near which there were no 

 egg clusters. These patches of favorable food afforded good traps 

 for the newly hatched caterpillars, which were being carried from the 

 infested woodlands 1 mile to the west, as did the tanglefooted screen 

 on which such large numbers were caught the same year. 



Seventy-seven egg clusters were found and creosoted in 1914 in the 

 same area as was scouted in 1913. Thus it will be noted that there 

 were slightly more than one-half the number of egg clusters found in 

 1914 as in 1913, in spite of the rigid control measures practiced during 

 the former year. The location of the beach with respect to the 

 infested woodland across the marshes was ideal for heavy reinfesta- 

 tion each year, and this condition prevails in apple orchards, wood- 

 lands, and shade trees that arc cleaned within the gipsy moth infested 

 area and become reinfested annually by means of the wind. 



OBSERVATIONS ON ISOLATED TREES AND YOUNG APPLE ORCHARDS 



FOR REINFESTATION. 



Twelve isolated trees in the midst of c.ultivatod fields and mowings 

 were selected in the early spring of 1914; (hose, were cleaned of egg 

 clusters, trunks tanglefooted, and later examined for reinfestation by 

 the wind. These trees were selected in towns about Merrimac, Muss., 



i Durii ol 191 1 15a f< ■■■ mall Infe tattoos were discovered In Vermont. 



