Jl. Stoyenoff et al., GYPSY-MOTH (LEPIDOPTERA, LYMANTRIIDAE) PERFORMANCE IN RELATION TO EGGHATCH AND FEEDING INITIATION TIMES, Environmental entomology, 23(6), 1994, pp. 1450-1458
We investigated performance for groups of gypsy moth that began feedin
g during different times in the spring and, thus, coincided with diffe
rent levels of host foliage maturation. The study was performed by cag
ing groups of newly hatched larvae on host foliage at three different
times over a 2-wk period. These times were coincident with the beginni
ng of natural gypsy moth egg hatch in the study area, near peak gypsy
moth egg hatch in that area, and near the end of gypsy moth egg hatch
for that area. At each establishment date, we placed the new groups of
larvae onto the same individual trees that we were using to feed the
earlier-established groups. Thus, the only host plant characteristics
that varied between the groups established on different dates were tho
se characteristics related to level of host foliage maturation. The tr
ee species we studied were red oak, white oak, bigtooth aspen, and tre
mbling aspen. Major findings include the following: larvae placed earl
iest had the highest mortality, slowest development times, and lowest
larval weights at the end of the season; larvae placed latest had the
lowest mortality, fastest development times, highest relative growth r
ates early on, and maintained the heaviest larval weights throughout t
he season; and effects of the various host species on gypsy moth growt
h and survival strongly support host effects seen in our earlier work
and the work of others on gypsy moth-host plant interactions. Aspen-fe
d insects had the highest larval growth rates at the end of the season
and were the heaviest pupae, although aspen-fed larvae had high level
s of mortality. Red oak-fed larvae had the best growth rates early in
the season and the worst growth rates late in the season.