First record of commensal flies, Desmometopa sp., on a dragonfly, Cordulegaster boltonii (Donovan) (Diptera: Milichiidae; – Anisoptera: Cordulegastridae)

The flies were seen near the mouth- parts of a perching and feeding 6 C. boltonii. They sucked from the prey being consumed by the dragonfly and dabbed its mouthparts after its meal, possibly cleaning them. During the dragonfly’s flight the flies probably rested on the lateral thorax. It seems likely, Cordulegaster was accompanied by Desmometopa at least for 20 min. Commensalism of adult Diplera on large predaceous arthropods has been so far reported in spiders, bugs and robber flies only.