A new pattern of parasitism in water mites (Hydrachnidia)? An insight into their relationships with pupae of caddisflies (Trichoptera).

To date, relatively few data have been available regarding the parasitism of water mite larvae on caddisflies; most available information relates to the adult stadia, fewer to caddisfly larvae, with just single references to pupae. The present paper examines the occurrence (phoresy and parasitism) of Piona stjordalensis larvae (119 individuals) on the larvae and pupae of Mystacides longicornis. It is possible that water mite larvae exhibit a new type of parasitism on caddisflies, with two consecutive parasitic larval stadia: one on the pupa, the other on the imago. [Display omitted] • First record of Piona stjordalensis (Hydrachnidia) on the aquatic stages of Mystacides longicornis (Trichoptera) is given. • This is the second identified case within water mites of such relationships as for caddisfly pupae in the literature. • 119 larvae of Piona stjordalensis were phoretic on caddisfly larvae, on pupae –phoretic and most of all parasitic. • On the caddisfly larvae, the water mites were attached only to the abdomen, on pupae – on all body parts. • Probably Piona stjordalensis exhibit a new type of parasitism on caddisflies, with two consecutive parasitic larval stadia. [ABSTRACT FROM AUTHOR]