REPORT OF CRANBERRY SUBSTATION FOR 1916. 225 



3 had sunk to the bottom, and 45 still clung to the leaves. They were 

 then taken from the water, and within seven hours 26 had nearly or en- 

 tirely recovered. 



On June 1, 152 worms from one-quarter to three-eighths of an inch long 

 were submerged on the leaves of an oak branch, as before, in 9 inches of 

 water. After thirty-eight and one-half hours of submergence, 46 floated 

 on the water, most of them being alive and active, 40 had sunk to the 

 bottom, and 66 still clung to the leaves. Those clinging to the branch 

 were then taken from the water and watched, and only a few ever showed 

 any sign of recovery. As a rule, the worms that came to the surface of 

 the water were among the largest of those submerged, as was also the 

 case in later tests, descriptions of which are not included here. 



The results of these experiments and of observations of bog flooding 

 operations, in which the small gypsy caterpillars behaved similarly, have 

 led the writer to the following conclusions : — 



1. That reflowing for this insect will be most satisfactory if done while 

 the worms are small and probably before the largest are more than five- 

 sixteenths of an inch long. The sooner it is done after the eggs are all 

 hatched the less will be the damage fr.om the feeding of the worms and 

 the less the trouble from their floating ashore alive, as it is evidently the 

 habit of the very young caterpillars to cling to their support when sub- 

 merged. 



2. To be entirely effective, even when the worms are small, a flowage 

 must probably be held nearly forty hours. 



Mr. C. W. Minott of the Bureau of Entomology of the United States 

 Department of Agriculture conducted some interesting investigations 

 during May and June, 1916, concerning the wind-spread of gypsy-moth 

 caterpillars on cranberry bogs. With his permission the following con- 

 densed account of these studies is given here : — 



Two bogs in Carver, Mass., were selected for experiments on wind dispersion, 

 namely, Muddy Pond bog, containing about 100 acres, and John's Pond bog, con- 

 taining about 44 acres (including pond). Six screens made of cotton cloth tacked 

 to a frame in two sections, each being 3 by 10 feet, were set up horizontally just 

 above the tops of the vines at various distances from the neighboring woodlands. 

 Each screen contained 60 square feet of cloth upon which " tanglefoot " was applied. 

 Daily examinations of each screen were made and data were taken concerning the 

 temperature and the direction and velocity of the wind during the dispersion period. 



The screens were located on the bogs at various distances, ranging from 400 to 

 1,200 feet, from woodland infestations. From one screen, located 600 feet from 

 infested woodland on the northwest and 900 feet on the west, 62 small caterpillars 

 were removed during the season, or shghtly more than 1 to the square foot. A 

 total of 143 small worms was wind-borne on to the six screens, which indicated 

 that an average of about 17,000 per acre blew on to the bogs. The infestations 

 around these bogs are as yet only medium in extent, this showing what may be 

 expected when the surroundings of bogs become thickly infested. ' 



1 Collins, C. W.: Methods used in determinihg Wind Dispersion of the Gipsy Moth and Some 

 Other Insects, Journal of Economic Entomology, Vol. 10, p. 174, 1917. 



