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 <i>Irenangelus punctipleuris</i> (Pompilidae: Ceropalinae) for the first time and that of <i>Dipogon</i> (<i>Nipponodipogon</i>) <i>nagasei</i> (Pompilidae: Pepsinae) as a complement to a previous study. The former species was found to parasitise <i>Auplopus carbonarius</i> and <i>A. pygialis</i> (Pompilidae: Pepsinae), while the latter species was found to parasitise <i>Di</i>. (<i>Deuteragenia</i>) <i>sperconsus</i> (Pepsinae). When using the well-established system of categories of brood parasitism in Pompilidae, <i>Irenangelus</i> corresponds to type A brood parasitism (‘highwayman’) and <i>Nipponodipogon</i> 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.