AbstractIn this study, we focused on the direct (i.e., predation) and indirect (i.e., potential threat from coexisting with a larger individual) effects of cannibalism and intraguild predation (IGP) during larval stages of two sibling ladybird beetles. These effects play an important role in the coexistence of the generalist–commonHarmonia axyridisand specialist–rareH. yedoensis(Coleoptera: Coccinellidae). Direct predation effect of cannibalism and IGP was asymmetric in the two sibling ladybird beetles; the fourth instar larvae ofH.axyridiswere better intraguild predators than cannibals, while the reverse was true in the larvae ofH. yedoensis. Neither cannibalism nor IGP significantly affected female body weight in either species. LarvalH.axyridissurviving exposure to cannibalism or IGP had a reduced number of ovarioles as adults, whereas adultH. yedoensisovarioles were not affected. For the indirect effects, longer developmental times in males and females and a lower total number of ovarioles in females were detected inH.axyridis. InH. yedoensis, shorter developmental time of males, lighter adult weight and fewer total ovarioles in females were observed. Olfactometer choice experiments clarified that the fourth instar larvae ofH.axyridisavoided the first instar conspecific larvae, while those ofH. yedoensiswere attracted to the odors fromH.axyridisand conspecifics. Thus,H.axyridishas an avoidance mechanism only for cannibalism but not for IGP,whereasH. yedoensisdoes not have any avoidance mechanism. These different behaviors in the direct and indirect effects of cannibalism and IGP observed in the laboratory may play important roles in the coexistence of generalist–commonH.axyridisand specialist–rareH. yedoensisin natural conditions, compensating for the large handicap ofH. yedoensisat reproductive interference fromH.axyridis.