M. Sjerps et P. Haccou, A WAR OF ATTRITION BETWEEN LARVAE ON THE SAME HOST-PLANT - STAY AND STARVE OR LEAVE AND BE EATEN, Evolutionary ecology, 8(3), 1994, pp. 269-287
Many insect species lay their eggs according to a clumped distribution
, which causes food shortage among the larvae. To avoid starvation, at
least some larvae have to migrate to another plant at some stage. Eve
n though this migration involves a high mortality risk, larvae (of, fo
r example, the cinnabar moth) often leave before their host plant is d
efoliated, thereby enabling others to remain safely on the plant. To u
nderstand why this remarkable behaviour has evolved, we modelled the s
ituation of two larvae on a small plant as a war of attrition. Our mai
n conclusions are that, in the case where the larvae are unrelated, th
ey should only migrate prior to defoliation in certain time periods, c
alled migration periods, when the pay-off of leaving decreases. Moreov
er, the optimal migration time is a random variable. When the pay-off
of leaving fluctuates, there can be several migration periods. In the
case where the larvae are related, it can also be optimal to migrate w
hen the pay-off of leaving increases. Relatedness increases the length
and the number of the migration periods, as well as the leaving tende
ncy during these periods. Furthermore, relatedness gives rise to a par
ent-offspring conflict over the optimal migration strategy.