Female swarming behaviour has rarely been described in Culicoides. Previous records of female swarms have only been described for females swarming in mixed swarms together with males. Two new observations of Culicoides swarms in Sweden are described here: A mixed swarm with females of Culicoides obsoletus/gornostaevae and males of C. gornostaevae, and a purely female swarm of C. impunctatus. Swarming behaviour can facilitate predator confusion. Swarming behaviour is therefore an evolutionary advantage that can explain mixed species swarms and purely female swarms.