THE GIPSY MOTH 0~N CRANBERRY BOGS. 15 
ited on the bogs during the previous season are destroyed ; and, second, 
by holding the flowage until after the maximum time of wind dis- 
persion has passed, which will result in drowning the young cater- 
pillars that fall in the water. It is probable that the low temperature 
of the water is an important factor in the death of the caterpillars. 
It may be desirable to hold the winter flowage late, say from the 1st 
to the 15th of June, in order to control the blackhead cranberry 
worm (Rhopohota naevana Hbn.). When this is found desirable, it 
is evident that the gipsy moth infestation may be controlled at the 
same time. It is also probable that some of the other cranberry in- 
sects may be controlled in combination with efforts against the gipsy 
moth. 
Observations have demonstrated that the maximum dispersion of 
first-stage larvae of the gipsy moth occurs about 13 or 14 days after 
the first hatching is noted, but this period varies with the season ; if 
there are 5 or 6 days when the temperature ranges from 75 to 85° F. T 
or higher, rapid hatching will occur, and if it continues quite warm, 
the larvae will reach the tops of trees sooner, resulting in an earlier 
dispersion. The best guide to determine when this may occur is the 
development of white oak leaves. When the leaf buds begin to un- 
fold it is safe to assume that the temperature has been high enough 
to cause hatching of gipsy moth eggs. 
Should the spring be late and the average temperature be low be- 
fore hatching, and continue so after hatching, then the dispersion 
period will be correspondingly delayed, and extended over a longer 
period ; in any case, however, there is a time of maximum dispersion, 
and this will occur, as stated, about 13 or 14 days after the first hatch. 
The closer the bog owner watches the upland conditions the better 
able he will be to control effectually an infestation on his bog. 
In control by flooding, only complete submergence is effectual. If 
through lack of sufficient water, or irregularities in the surface of 
the bog, there are sections where a considerable number of vine termi- 
nals are out of water (as shown in the right center of Plate V, Figure 
2, and to a less degree through the central section) , even with a light 
to medium infestation on a bog these terminal shoots become actual 
life rafts for hundreds of larva? that have crawled up the vines as the 
flooding gradually progressed, or reached them as the larva? were 
blown over the surface of the water by the wind. When any con- 
siderable number of these terminal shoots project above the water 
it is imperative that the larva? be brushed from the vines by using 
a common hand hayrake, drawing and pushing the vines under 
water several times with the back of the rake head. Unless this is 
done, there is likely to be considerable damage on these partially 
submerged sections of the bog. In the immediate foreground and 
