371 
1916-17.] The Family Chermesiche. 
about seven days. The third moult gave two forms — a nymph of the 
sexupara, and a fourth-stage progrediens. The apterous progredientes 
became adult during the first half of June and laid twenty to thirty 
brownish eggs under the protection of copious “ wool.” These eggs hatched 
in fifteen to twenty days. The proportion of sistens and progrediens larvae 
in the progeny of this and succeeding generations was variable. The 
ancestry of these females, i.e. whether derived from gallicolae migrantes or 
from sistentes of previous years, may be a factor causing this variability, 
but this can only be determined by control experiments extending over 
many years. One factor, however, seemed to be the climatic conditions. 
In the summer of 1916 the percentage of progrediens larvae was mucli 
higher than in the summer of 1917, with the result that the individuals of 
Generations II and III of the progredientes were more numerous in the 
former than in the latter summer. The larvae, hatching from the eggs laid 
by Generation I, were in most cases principally of the progrediens type. 
In some cases, however, the proportion was about half and half, while in 
one experiment the progeny consisted entirely of sistentes. The females 
of Generation II became adult during the second half of July. The 
progeny of Generation II was as I, but the average percentage of sistentes 
was higher. The females of Generation III became adult about the 
beginning of September. The percentage of sistentes in the progeny of 
this generation was still higher than the preceding generation. The 
inclement weather caused the death of the progrediens larvae in the first 
or subsequent stages. In each generation the sistens larvae remained un- 
developed and hibernated, while the progrediens larvae developed. Only 
three moults were observed in progredientes, Generations II and III, 
while four is the normal number in the progrediens type. Further 
research is necessary to clear up this point. 
Generation IV. Sexupara . — The adult stage was reached during the 
second half of June. The sexuparae were transferred to spruce; they 
settled principally on one- to three-year-old needles. Five to ten yellow 
brown eggs were laid under the protection of the wings and copious 
“ wool.” 
Generation V. Sexuales . — The eggs hatched in ten to fifteen days. 
The larvae were straw-coloured, and lived under the “ wool ” and 
wings. The four moults took place at intervals of five to seven days. 
The adult stage was reached during the second half of July. The 
female laid the single fertilised egg under a bark scale near a shaded bud. 
The egg was straw-coloured. This egg hatched in twenty to twenty- 
five days. 
