THE GIPSY MOTH OX CKAXBEERY BOGS. 11 



considered as a continuous record from 3.45 a. m. until 7.30 p. m. 

 These observations determined that feeding- began soon after day- 

 light, gradual!}' increasing as the temperature increased, until it 

 reached its maximum from 9 to 11 a. m. when it began to diminish, 

 reaching a minimum during the midday, then gradualh^ increas- 

 ing again, reaching its maximum from 3 to 5 p. m., and gradually 

 decreasing after this hour, a majority of the larvae seeking shelter 

 on the underside of the leaves by 7 p. m. Wind dispersion records 

 cited show practically no movement of small caterpillars between 

 11 a. m. and 3 p. m., the period when there is practically no feeding 

 and very little activity. 



INJURY BY A GIVEN NUMBER OF LARV^. 



When a new cranberry bog is planted the vines are usually set in 

 rows 12 inches apart, and the same distance in the row. The in- 

 crease of the vine area is by runners radiating out from each plant. 

 in all directions, eventuallj^ forming a dense mass of vines over the 

 whole bog surface. From these runners upright shoots grow, and 

 under normal conditions increase in height by growth from a ter- 

 minal bud, and it is upon this new growth that the fruit is borne 

 each season. It is evident that any injury to the terminal buds re- 

 duces the amount of fruit in proportion to the number of buds de- 

 stroyed. With the object in view of obtaining some definite infor- 

 mation on this question an experiment Avas undertaken to determine 

 the amount of damage to cranberry vines that would result from a 

 heavy infestation of gipsy moths. Three pens were built 3 feet 

 square, inside measurement, with sides 2^ feet high. On the out- 

 side of each pen, 6 inches from the top, four strips of board were 

 attached at an angle of 30 degrees. Each pen was then forced into 

 the bog about 6 inches and the sand firmly tamped both inside and 

 outside of pens to prevent escape of larvae. On the underside of this 

 overhang and 6 inches from the top on the inside of each pen bands 

 of commercial sticky tree-banding material were applied in order to 

 prevent the escape of larvae that were placed on the square yard of 

 vines inclosed and to prevent other insects from gaining entrance to 

 the pen. (PI. V, Fig. 1.) 



From year to jesiT during the period covered by these studies 

 varying numbers of first-stage larvae have been placed in these pens 

 each season and the injurj^ to the vines, as well as the feeding habits 

 of the larvae on cranberry foliage, has been carefuly noted. 



The results of these experiments have shown that an infestation 

 of two larvae to the square foot has destroyed nearly all the new 

 growth of cranberrv foliage. An infestation averaging one larva 



