First report of interspecific facultative social parasitism by Polistes sp. on Polistes djakonovi Kostylev (Hymenoptera: Vespidae) in South Korea

Social parasitism is occasionally found in some Polistes and Vespa species, such as Vespa dybowskii. We report a discovey of interspecific facultative social parasitism by Polistes sp. (possibly P. mandarinus) on Polistes djakonovi Kostylev in two rural areas of South Korea. P. djakonovi is very similar to Polistes sp. in its body color patterns except that the mark on the clypeus is different. In nest 1 (65 cells), we found 5 females of P. djakonovi and 4 females of Polistes sp. on 30 July 2014, whereas nest 2 (102 cells) contained 12 females and 16 males of P. djakonovi, and 3 females of Polistes sp. on 28 August 2013. Although we found the two nests in July and August, P. djakonovi seems to have been exploited by Polistes sp. at the end of the preemergence period (early to mid-June). The two nests found in this study had mainly white cocoon caps of P. djakonovi with several yellow ones of Polistes sp. In most cases of social parasitism, intruders have a larger size of the body or some body parts than the host in order to usurp the host; in contrast, this study showed that the hosts had lager bodies than the intruders.