18 BULLETIN 273, U. S. DEPARTMENT OF AGRICULTURE. 



where there was a general infestation. Some of them were later dis- 

 carded owing to the discovery of overlooked egg clusters that had 

 hatched. On the trees retained there were from 2 to 8 and in one 

 case 11 large caterpillars above and below the tanglefoot, indicating 

 that there was reinfestation by the wind. The top of a medium to 

 large sized apple tree would offer more resistance to the wind than 

 did the screen on the Merrimac standpipe, upon which was lodged 

 approximately one first-stage caterpillar to every square foot of wire 

 exposed. 



Some further observations confirming these conclusions were made 

 by Mr. C. E. Hood in July, 1914, in two young apple orchards in 

 Merrimac (PL VI) and West Newbury, Mass. These orchards were 

 2 and 4 years old, respectively, and clean cultivation was practiced 

 in them. A large number of the trees were examined in the center 

 of these orchards, which were in some cases 500 yards from the 

 nearest infestations on larger trees. Thirty-four large larvae were 

 found in selected areas of the two orchards, not more than one of 

 which appeared on a single tree. No egg clusters could be found, 

 and it was concluded that the infestation was due to windspread. 



Mr. J. V. Schaffner, jr., has also reported a similar incident from 

 Dover, Mass. 



SMALL LARV.E BLOWN INTO THE OCEAN ANNUALLY FROM INFESTED 

 WOODLANDS NEAR THE COAST. 



At the rate of 266 first-stage larvae caught on 450 square feet of 

 tanglefooted wire at Salisbury Beach in 1913 (being located 1 mile 

 from the nearest infested woodland), a basis is given for estimating 

 the huge numbers borne into the ocean each year. At the same 

 ratio a continuous screen 1 mile long and 6 feet high would have 

 caught 18,726 larvae. Judging from the altitude, 300 feet above sea 

 level, where quantities were caught at Merrimac, Mass., it is apparent 

 that this number should be fifty times as much, or 936,300 per mile. 

 There is now upwards of 450 miles of coast line infested in New 

 England (PL VII), and figuring that general spread by wind occurs 

 over one-half of this distance, the ocean swallows up annually over 

 210,000,000 small larvae. The number is probably much greater 

 than is here indicated, as it is not known how many of the small 

 larvae passed through the wire meshes of the screen which is used as 

 a basis for these figures. 



These calculations, which are partly theoretical, serve to indicate 

 what might have been the result with regard to the area infested had 

 the moth first been introduced 100 miles farther westward than Med- 

 ford, Mass. It also emphasizes the necessity of keeping this moth 

 confined to New England territory, if rapid and general spread over 

 the United States is to be prevented. 



