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



It will be noted, according to the records taken on Lunging Island, 

 that nine larvae came from the southwest, that is, from Plum Island, 

 13^ miles away. The weather records at the latter place indicate 

 that conditions were such that at least 18 of those caught on the 

 screen at Lunging Island came from Plum Island, or more distant 

 points in that direction. 



Thirteen and one-half miles is the maximum record for distance 

 that larvss have been carried by the wind in all experiments thus far 

 conducted by us, yet it is probable that the limit has not been reached. 

 The locations for securing such records, together with, suitable con- 

 ditions with reference to infestations, are rare. 



DISPERSION EXPERIMENTS ON THE HILLS OF NEW HAMPSHIRE IN 1913 



AND 1914. 



In the scouting operations conducted by Mr. L. H. Worthley in the 

 outside territory infested by the gipsy moth, numerous infestations 

 were being found on hilltops. It could not be ascertained whether 

 tliis spread was the result of the wind, vehicles, or other possible car- 

 riers — man or animals. These hills contained woodlands, orchards, 

 pastures, mowings, and roads over which there was more or less 

 travel, making spread possible artificially. Thinning was practiced 

 in these infestations, egg clusters were creosoted, and bands of 

 tanglefoot were placed on the trees to keep the first-stage cater- 

 pillars hatching near the ground from ascending the trees, thereby 

 decreasing their chances of spread by the wind. 



To investigate the source of these hilltop infestations, one hill was 

 selected in each of four towns in New Hampshire, namely, Andover, 

 Henniker (PI. IV, fig. 2), Hillsboro, and Troy, and large screens 

 erected thereon as traps for the small caterpillars. (See also Plate 

 VII.) It seemed desirable to know if these colonies were the result 

 of windspread, and whether caterpillars were being carried from hill- 

 top to hilltop, valley to hilltop, or vice versa, so that scouting and 

 control methods could be changed accordingly. 



The screens were constructed of f-inch mesh poultry wire 3 feet 

 wide. This was stapled to posts set in the form of a T. The 

 posts were about 12 feet high and guyed with No. 13 wire. The 

 wire was fastened in two widths, one above the other, making a 

 screen surface 6 feet wide. The top selvage ranged from 10 to 12 

 feet from the ground owing to the level of the land. The screens 

 were erected with one wing 35 feet long, facing the north and south, 

 and another, 40 feet long, facing east and west. The total number 

 of square feet exposed to the winds in each screen was 450. 



There were known infestations one- third to two miles in all directions 

 from the screens in the foregoing towns, but negative results were 



