An army of one: predaceous diving beetle life history stages affect interactions with shared mosquito prey

Predators with complex life cycles often differ in their morphology, behavior, and trophic position across their ontogeny, and may thus have variable effects on shared prey. We used the predaceous diving beetle Laccophilus fasciatus rufus as our predator, whose larvae and adults often co-occur in freshwater lentic systems. As a shared prey we used early and late instar Culex quinquefasciatus, a common wetland mosquito. We found that single adult predators were more likely to consume late instar prey compared to juvenile predators, who ate early and late instar prey equally. A mixture of juvenile and adult predator stages led to higher consumption of prey when compared to either predator type alone. Adult dytiscids consumed three times as many dead prey compared to living ones, thus implying a role in scavenging for this life-history stage. Our work highlights that predators with complex life-history stages may affect shared prey in complicated and unpredictable ways.