Generalists and specialists of brood parasitism in spider wasps (Hymenoptera: Pompilidae)

Based on emergence records from trap nests and naturally occurring nests, we determined the brood parasitism behaviour of Irenangelus punctipleuris (Pompilidae: Ceropalinae) for the first time and that of Dipogon (Nipponodipogon) nagasei (Pompilidae: Pepsinae) as a complement to a previous study. The former species was found to parasitise Auplopus carbonarius and A. pygialis (Pompilidae: Pepsinae), while the latter species was found to parasitise Di. (Deuteragenia) sperconsus (Pepsinae). When using the well-established system of categories of brood parasitism in Pompilidae, Irenangelus corresponds to type A brood parasitism ('highwayman') and Nipponodipogon corresponds to type B brood parasitism ('sneak thief'). In comparison with brood parasitism in birds, we propose new concepts, namely 'generalists' and 'specialists' of brood parasitism, which correspond to type A and type B brood parasites, respectively. We discuss the differences in behavioural patterns and morphological features between the two types. We also confirm the proposed concepts by their molecular phylogenetic positions.