Between mosquitoes and stoneflies: Observation of Plecoptera nymphs preying on chironomid larvae (Diptera)

Plecoptera is an order of aquatic insects, the immature stage of which inhabits preserved, fast-flowing, well oxygenated streams and is a predator that feeds on many aquatic groups. Prey preference is determined by the active choice of the predator or by the vulnerability of the prey and the balance of energy spent searching for and manipulating the prey. Analysis and observation of predator-prey events provide a greater understanding of the mechanisms governing this interaction. The stream in which predation was observed is located in the forest region of the Cajari River RESEX (Amapá, Brazil). The specimens were collected using a rapiché (D-net) in September 2023. The event observed was the predation of a Chironomidae larva by a nymph of Macrogynoplax Enderlein (Perlidae, Plecoptera), in a preserved stream. The action of these predators contributes to controlling the abundance of Chironomidae larvae. This observation proves the quality of the ecosystem and its effectiveness in maintaining sensitive individuals, such as Plecoptera, as well as tolerant ones, such as the majority of Chironomidae, to the point of allowing their usual behavioral patterns to unfold.