A note on phototactic behavior and on phoretic associations in larvae of Mecistogaster ornata Rambur from northern Costa Rica (Zygoptera: Pseudostigmatidae)

A larva was found covered with algae on the dorsal side of the head, thorax, abdomen and caudal gills. The larvae showed a phototactic behavior, using the caudal gills to follow a gradient of light, which also corresponded to a gradient of oxygen. Larval Chironomidae were found between the wing cases and over the algae of the gills. Relationships between odonates and chironomids are discussed.