Bk. Agarwala et H. Yasuda, Overlapping oviposition and chemical defense of eggs in two co-occurring species of ladybird predators of aphids, J ETHOL, 19(1), 2001, pp. 47-53
Oviposition behavior in two co-occurring species of predatory ladybirds of
aphids were investigated. The two species of beetles often shared the same
aphid colonies in bean plants in space and time and showed a similar ovipos
ition pattern in response to aphid abundance. Overlapping oviposition prese
nts potential risks of interspecific predation of eggs in unstable aphid co
lonies. Eggs in clusters by two ladybird species, Menochilus sexmaculatus a
nd Coccinella transversalis, were defended from reciprocal predation and th
e defense was found to be chemical. Eggs occurring singly were found to be
highly vulnerable to predation. Strength of chemical defense significantly
increased from single eggs to eggs in mixed clusters and eggs in pure clust
ers. Results are not only consistent with the hypothesis that eggs in clust
ers are better protected from natural enemies but also extend the ambit of
the hypothesis that coexisting ladybird predators have evolved to avoid the
risks of heterospecific predation of eggs in a patch.