Attack, escape and predation rates of larvae of two aphidophagous ladybirds during conspecific and heterospecific interactions

The attack, escape and predation rates for larvae of aphidophagous ladybird Propylea dissecta (Mulsant) and Coccinella transversalis Fabricius were quantified as a potential mechanism leading to the differences in the incidence of cannibalism and intraguild predation. These rates were compared at four larval instars within and between the species. The attack rates of larvae of C. transversalis were significantly higher than those of P. dissecta towards conspecific and heterospecific victims. For both species, third instars exhibited maximum tendency to attack. Escape rates in C. transversalis were higher than P. dissecta. In P. dissecta, the second instars made a greater number of escapes than other conspecific instars after being attacked by same stage cannibal or heterospecific predator. In P. dissecta, first instars suffered maximum mortality due to cannibalism and intraguild predation by conspecifics and heterospecifics of the same and older developmental stage. No larvae of C. transversalis were eaten by P. dissecta of the same stage. These results suggest that the larvae of P. dissecta were more often potential cannibals than intraguild predators, while the reverse was the case in C. transversalis. Based on this finding, it could be predicted that in patchy prey habitats, high rates of larval cannibalism in P. dissecta would occur with a high risk of cannibalism of first instars. Larvae of C. transversalis would respond as intraguild predators, while those of P. dissecta as intraguild prey. The greater size and walking activity of C. transversalis could be possible reason for this tendency.