Commensalism between Corydalus Latreille, 1802 (Megaloptera, Corydalidae) and Corynoneura Winnertz, 1846 (Diptera, Chironomidae, Orthocladiinae) larvae was recorded in Indaiá stream, at 1,380 m a.s.l. (Parque Nacional da Serra do Cipó, 19º-20ºS, 43º-44ºW) and in the headwaters of São Francisco river, at 1,300-1,700 m a.s.l. (Parque Nacional da Serra da Canastra, 20º00'-20º30'S, 46º15'-47º00'W), in Minas Gerais state, Brazil. Seventy eight Corydalus larvae (range 22-88 mm) were sampled: 61 in the Indaiá stream and 17 in other two streams. Twelve Corydalus larvae (22-79 mm) in the Indaiá stream and three out of 15 larvae in the headwaters of São Francisco river (38-50 mm) had Corynoneura, larvae and pupae on their gills (3rd to 6th) and a few larvae attached to the abdominal segments of larger Corydalus larvae (> 25 mm). Sixty-nine larvae of Corynoneura were found in the regurgitated material from Corydalus. It is remarkable that by attaching to larger body size predators, prey could become free from predator bouts and could also be transported by them.
Headwater stream; phoresy; predator-prey relationship; São Francisco river
