Notes on the prey, nesting behaviour and natural enemies of threeBembixsand wasps (Hymenoptera: Crabronidae) in the Iberian Peninsula

Abstract

Abstract. Bembix is a cosmopolitan genus with more than 300 species distributed all over the world. The females of these wasps dig burrows in the ground and hunt for fl ies to feed their larvae. Current knowledge of the nesting behaviour of most Palaearctic species (around 50) is limited. In this study, we provide data on the nest structure, nesting activity, natural enemies and prey captured by three Bembix sand wasps present on the Iberian Peninsula: B. zonata, B. fl avescens bolivari and B. merceti. We also analyze the prey spectrum of the three species, comparing our data with those available from previous studies. B. zonata exhibits the greatest selectivity index (and the narrowest niche width), capturing mainly Syrphidae to provision its nests. B. merceti shows the greatest niche width in comparison with the other two species. The inter-annual differences in the diet of B. merceti are important and are probably due to the ability of this wasp to change from one prey resource to another, depending on its availability.Résumé. Notes sur les proies, la nidifi cation et les ennemis naturels de trois espèces de Bembix (Hymenoptera : Crabronidae) de la péninsule Ibérique. Le genre Bembix est cosmopolite avec plus de 300 espèces à travers le monde. Les femelles creusent des terriers dans le sol et capturent des diptères qui servent de provision à leurs larves. Les connaissance actuelles sur le comportement de nidifi cation de la plupart des espèces européennes (ca 50) sont assez limitées. Dans le présent travail, les auteurs abordent la structure du nid, l'activité de nidifi cation, les ennemis naturels et les proies capturées par 3 espèces de Bembix présentes dans la péninsule ibérique: B. zonata, B. fl avescens bolivari et B. merceti. Ils analysent également le spectre des proies des trois espèces et le comparent aux études antérieures. B. zonata, qui présente le plus grand indice de sélectivité et la niche la plus étroite, utilise surtout des Syrphidae comme proies. B. merceti présente la niche la plus large par rapport aux deux autres espèces. Les différences inter-annuelles dans le régime alimentaire de B. merceti sont importantes et sont probablement dues à la faculté qu'a l'espèce de passer d'un type de proie à l'autre selon les ressources disponibles.

Low Host Specialization in the Cuckoo Wasp, Parnopes grandior, Weakens Chemical Mimicry but Does Not Lead to Local Adaption

“…As expected by its wide host range with at least 10 species of Bembix [2,[19][20][21][22][23][24][25], the chemical mimicry of P. grandior could not be as precise as in other cuckoo wasp species which are either specialised in attacking a single host (C. mediata and P. neglecta) or have strong preference to one of only two hosts (H. rutilans) [11,17]. Our results may resemble more what was previously found in H. nobile and its host C. arenaria [11], probably because H. nobile is known to attack at least four Cerceris species [23,53].…”

“…Females of many insect brood parasites sneak into the host nests in order to deposit their eggs or larvae, a behaviour allowing parasites to easily leave chemical traces in the nests. These cues may provoke a defensive response by the hosts, i.e., the abandonment of the nest, the destruction of the parasites' eggs or direct attack to the adult parasite [1][2][3]. Thus, to reduce the probability of being detected by their hosts during nest invasion, insect brood parasites have evolved different strategies that often prevent recognition via chemical cues [4][5][6][7].…”

“…Here, we studied the cuckoo wasp, Parnopes grandior (Pallas, 1771). At least 10 Bembix (Hymenoptera: Crabronidae) species are recorded as hosts of this cuckoo wasp [2,[19][20][21][22][23][24][25], suggesting that it is a brood parasitoid specialist at the genus level. Bembix wasps are Diptera-hunting predators that nest in aggregations in sandy soil, where P. grandior often co-occurs [26].…”

“…Parnopes grandior females oviposit in the host nests during these provisioning flights of host females [24,25]. While host females are able to detect eggs of P. grandior, and, in consequence, abandon their nests [2], cuckoo wasps would be favoured to chemically mimicking their hosts, preventing them from leaving chemical cues.…”

Complex-to-Predict Generational Shift between Nested and Clustered Organization of Individual Prey Networks in Digger Wasps

“…B. merceti females were individually marked with combinations of three colour dots on the thorax, using marking pens with fast drying inks (water-based paint) [48] , [49] and weighed in the field with an Ohaus Scout Pro scales (±0.001 g). To avoid potential statistical problems derived from low sample sizes, only females with≥4 prey captured (10 females in 2008, 14 in 2009 and 12 in 2010) were included in the analyses [20] .…”