Behaviors of the midge, <i>Cricotopus</i> (Diptera: Chironomidae) related to Mutualism with <i>Nostocparmelioides</i> (Cyanobacteria)

Abstract

Behaviors of Cricotopus nostocicola (Wirth) related to its mutualistic interaction with Nostoc parmelioides Kutzing were explored. The late instars and pupae probably always remain inside their Nostoc colony until emergence. Laboratory observations of 4th instar larvae removed from Nostoc colonies showed that only 65% of the midges were able to re‐enter their colony after 20 hours in still water, although placed less than 5 cm away, and midge larvae could move at only 8.9 mm h‐1 in still water. This suggests larvae would not be able to survive if they left their colony. Midge larvae attached their colonies tightly to rocks and may use this ability to orient their colony with respect to flow. Pupation occurred at the same time host Nostoc colonies formed hormogonia (the dispersal stage of Nostoc) and at the same time many new, uninhabited colonies appeared. The replication of both taxa occurred simultaneously, and may have been beneficial to both.