I study the evolutionarily stable seasonal patterns of hatching and pu
pation for herbivorous insects that engage in exploitative competition
for a renewable resource. A longer larval feeding period enhances fem
ale fecundity, but also causes a higher mortality by predation and par
asitism. Previously, it was shown that the evolutionarily stable popul
ation exhibits asynchronous starting and ending of the larval feeding
period in a model in which larval growth rate decreases with the total
larval biomass in the population due presumably to interference compe
tition. Here I study the case in which resource availability changes n
ot only with environmental seasonality but with the depletion by the f
eeding of larvae. I find that if the impact of the herbivory is strong
, both hatching and pupation should occur asynchronously in the evolut
ionarily stable population. And if the favourable season for the host
plant is short the ESS population may include synchronous timing of pu
pation. If the timing of hatching and pupation occurs asynchronously,
in the first day of each interval some fraction of the population hatc
h or pupate, respectively and the rest do so gradually over the interv
al. In addition, if the environmental variable changes as a symmetric
function of time, the length of the period in which hatching occurs te
nds to be much shorter than the period in which pupation occurs.