The effects of three sympatric ladybird species on oviposition by Menochilus sexmaculatus (Coleoptera: Coccinellidae)

Oviposition site selection has a strong impact on the spatial distribution and sustenance of a species. This site selection by ladybirds (Coleoptera: Coccinellidae) is known to be well mediated amongst other factors by the oviposition deterring pheromones present in conspecific larval tracks. It would be also useful to the organism to be sensitive to heterospecific larval tracks, to protect from intraguild predation; however, this has not yet garnered much attention and there are only a few scattered studies with ambiguous results. The present study thus investigates the oviposition deterring effects of heterospecific presence and semiochemicals of heterospecific life stages (eggs, fourth instar larvae, pupae, adult males and females) of ladybird species, viz. Coccinella septempunctata, C. transversalis, Propylea dissecta on females of Menochilus sexmaculatus. Results reveal that the presence of all heterospecific life stages inhibits oviposition of M. sexmaculatus and the inhibition is density dependent. Semiochemicals of eggs, larval and adult tracks also show density-dependent inhibitory effects. The semiochemical-induced oviposition inhibition was stage specific with respect to the degree of inhibition. Of all heterospecific species tested, maximum and minimum oviposition deterrence of M. sexmaculatus was against C. septempunctata and P. dissecta, respectively. Comparison of our previously published results on oviposition inhibition in M. sexmaculatus due to conspecific presence with the current ones revealed increased inhibition in conspecific presence than heterospecific indicating ability to differentiate.