Effect of victim relatedness on cannibalistic behaviour of ladybird beetle, Cheilomenes sexmaculata Fabricius (Coleoptera: Coccinellidae)

Cannibalism is taxonomically widespread and has a large impact on the individuals' fitness and population dynamics. Thus, identifying how the rates of cannibalism are affected by different ecological cues is crucial for predicting species evolution and population dynamics. In current experiment, we investigated how victim relatedness affects the cannibalistic tendencies of different life stages of ladybird, Cheilomenes sexmaculata, which is highly cannibalistic. We provided larval instars and newly emerged adults of C. sexmaculata with a choice of sibling, half-sibling and non-sibling conspecific eggs as victim of cannibalism. First victim cannibalised and latency to cannibalise were observed along with total number of victims cannibalised after 24 h. First preference of victim did not differ with life stages of the cannibals though the number of victims cannibalized did increase with advancement in stage. Percent egg cannibalism also varied significantly with life stage and victim relatedness. First and second instars tend to cannibalise more percentage of sibling and non-sibling eggs while third instars cannibalised more percentage of non-sibling eggs; fourth instars and adults on the other hand cannibalised highest percentage of eggs irrespective of their relatedness. Insignificant effect of victim relatedness was observed on latency to cannibalise eggs, though it varied significantly with the cannibal's life stage. Shortest latency to cannibalise was recorded for first instars and longest for adults and second instars. In conclusion, kin recognition and avoidance of cannibalism is stage-specific, with fourth instar and newly emerged adults being less discriminatory as compared to early stages owing to increased evolutionary survival pressure.