8 BULLETIN 1032, U. S. DEPARTMENT OF AGRICULTURE. 
another by these leaves drifting from place to place over the bog in 
and on the water which sometimes collects during the winter time. 
Instances were noted in which numerous egg-bearing leaves had been 
washed into a corner of a bog. where they almost covered the vines. 
These eggs, being the first affected by rising temperatures, were the 
first to hatch in the spring, and the young larvse had almost com- 
pletely destroyed the surrounding uprights before eggs elsewhere in 
the bog had hatched. 
Incubation and Hatching. 
The first signs of incubation are noted as the black head and tho- 
racic shield of the developing larva begin to show through the chor- 
ion or eggshell. As development progresses the young larva may be 
seen to move within the egg and finally, as it grows in vigor, to rup- 
ture the egg wall at a point over its mandibles and gradually escape 
by means of a wriggling sidewise motion through this slitiike open- 
ing, which is near the top of the upper surface of the egg. (Fig. 
1. h. c.) It usually takes from about 3 to 5 minutes for the larva to 
free itself entirely from the eggshell. 
FACTOES iNFTrENCING HATCHING AND DEVELOPMENT. 
(a) Temperature. — Temperature has the greatest influence on the 
fireworm eggs as well as on the other stages. This varies more than 
is generally supposed among different bogs, depending upon location. 
(h) Depth of vines. — Another very important factor which tends 
to retard or hasten development of fireworm eggs is the depth of the 
vines in which they are deposited. A bog with thin vines will warm 
up more readily in the spring and maintain a higher temperature 
generally throughout the season than a bog with rather thick vines. 
Observations show, for instance, that on bogs with thin vines, hatch- 
ing generally starts during the first warm days of spring (sometimes 
late in March or in early or mid- April), reaches its maximum early 
(say towards the latter part of April), and produces moths in maxi- 
mum numbers in the middle or late part of June. On a thickly vined 
bog., in the same locality, however, and under similar conditions of 
temperature and moisture, hatching, while it may start about the 
same time as it does on the thinly vined bog, will be only desultory 
until the vines have warmed up considerably. Hatching in maximum 
numbers may not take place then until the middle or latter part of 
May. This in the absence of a winter flooding distributes hatching, 
on bogs witli a medium or heavy growth of vines, over a considerable 
period. 
(c) Drainage. — During the winter or rainy season more or less 
water usually accumulates on the majority of the cranberry bogs 
