The cuticle of certain insect body parts can be hardened by the addition of metals, and because niche separation may require morphological adaptations, inclusion of such metals may be linked to life history traits. Here, we analysed the distribution and enrichment of metals in the mandibles and ovipositors of a large family of gall-inducing wasps (Cynipidae, or Gall-Wasps) (plus one gall-inducing Chalcidoidea), and their associated wasps (gall-parasitoids and gall-inquilines) (Cynipidae, Chalcidoidea and Ichneumonoidea). Both plant types/organs where galls are induced, as well as galls themselves, vary considerably in hardness, thus making this group of wasps an ideal model to test if substrate hardness can predict metal enrichment. Non-galler, parasitic Cynipoidea attacking unconcealed hosts were used as ecological “outgroup”. With varying occurrence and concentration, Zn, Mn and Cu were detected in mandibles and ovipositors of the studied species. Zn tends be exclusively concentrated at the distal parts of the organs, while Mn and Cu showed a linear increase from the proximal to the distal parts of the organs. In general, we found that most of species having metal-enriched ovipositors (independently of metal type and concentration) were gall-invaders. Among gall-inducers, metals in the ovipositors were more likely to be found in species inducing galls in woody plants. Overall, a clear positive effect of substrate hardness on metal concentration was detected for all the three metals. Phylogenetic relationships among species, as suggested by the most recent estimates, seemed to have a weak role in explaining metal variation. On the other hand, no relationships were found between substrate hardness or gall-association type and concentration of metals in mandibles. We suggest that ecological pressures related to oviposition were sufficiently strong to drive changes in ovipositor elemental structure in these gall-associated Hymenoptera.

Land-use change, including urbanization, is known to affect wild bee (Hymenoptera: Apoidea) diversity. However, while previous studies have focused on differences across local urbanization gradients, to the best of our knowledge, none focused on differences among cities at a wide geographical scale. We here used published data for wild bee communities in 55 cities across the globe, in order to explore how city traits (population density, city size, climate and land-use parameters) affect both taxonomic (diversity, distinctness, dominance) and functional (body size, nesting strategy, sociality, plant host specialization) profile of urban bee communities. By controlling for sample size and sampling effort, we found that bigger cities host few parasitic and oligolectic species, along with more above-ground-nesting bees. Cities with highly fragmented green areas present a lower proportion of oligolectic species and a higher proportion of both social species and large-bodied bees. Cities with more impervious surfaces seem to host a lower proportion of below-ground-nesting bees. Hotter cities present both a lower richness and diversity, with functional diversity highest at intermediate precipitation values. Overall, it seems that high levels of urbanization—through habitat modification and the “heat island” effect—lead to a strong simplification of the functional diversity of wild bee communities in cities. Our results may help explain the previously observed variable response of some bee community traits across local urbanization gradients.

Aim of study: The globally invasive gall wasp, Dryocosmus kuriphilus Yasumatsu, 1951 (Cynipidae: Cynipini), reached Spain seven years ago and is already regarded as an important pest of chestnuts (Castanea spp.) in this country as well as worldwide. In this paper, we present comprehensive data on the establishment in Spain of Torymus sinensis Kamijo, 1982 (Chalcidoidea: Torymidae), an effective non-native natural enemy of this pest, as a result of both natural dispersal and settlement after controlled releases since 2015.Area of study: Sites of the Spanish autonomous communities of Galicia, Asturias, Basque Country, Catalonia, Andalusia and Madrid where D. kuriphilus is present.Material and methods: To study the natural dispersal of T. sinensis from France, we selected two sampling sites in Catalonia, six in the Basque Country and two in Navarra known for their heavy Asian chestnut gall wasp (ACGW) infestation; to study T. sinensis establishment after authorized controlled releases by the concerned authorities, the field samplings were done mainly in Galicia (35 sites) and Andalusia (8 sites). Additionally an experimental release study was made in Madrid.Main Results: Our results showed that T. sinensis has spread throughout Spain by natural dispersal across the French border and now occurs in Catalonia (two sites), the Basque Country (three sites) and Navarra (one site) but not in the neighbouring region of Cantabria. The percentage of parasitism by T. sinensis on D. kuriphilus is higher in the Basque Country sites, which are close to the French border, thus indicating that its establishment in these localities is not recent. After controlled releases, T. sinensis has been successfully established in five release sites in Andalusia (Valle del Genal and Sierra Blanca, Málaga Province) and one release site in Madrid. However, in the region of Galicia (NW Spain), where the number of authorized releases has been higher, the establishment of T. sinensis still appears to be very low.Research highlights: Established populations of T. sinensis may exert a positive buffer against D. kuriphilus-driven chestnut infestation in Spain, similar to what is observed in other invaded European countries.Additional Keywords: Controlled releases, Torymidae, invasive species, Cynipidae, natural spread, biological control.Abbreviations used: Asian chestnut gall wasp (ACGW); Torymus sinensis parasitism rate (TsPR); mean of ACGW larval chambers per gall (MACGW).