Melittobia parasitoid wasps (Hymenoptera: Eulophidae) in the Iberian Peninsula: new data on distribution, biology and morphology

Summary: Most data about parasitoids of the genus Melittobia (Hymenoptera: Eulophidae) in Europe, where only the native M. acasta (Walker, 1839) and the alien M. australica Girault, 1912 occur, come from studies carried out in the central-northern part of the continent. In the present study, we provide new information on both species in the Iberian Peninsula. We obtained M. acasta from mud nests of Sceliphron destillatorium (Illiger, 1807) (Hymenoptera: Sphecidae) and both M. australica and M. acasta from nests of Sceliphron spirifex (Linnaeus, 1758). Melittobia australica records are the first for this allochthonous species in the Iberian Peninsula, which is the second record in Europe. Rate of parasitism (number of parasitized nests/total number of collected nests) reached almost 50% of nests for M. australica and was much lower for M. acasta (up to 6%). The probability of M. australica to be found in a host nest did not depend on the number of brood cells in the nest, suggesting that nest size does not affect parasitism. Scanning electron microscope (SEM) images provided new information about the morphology of the antennal sensory system of both species. Energy-dispersive X-ray spectroscopy (EDS) revealed the presence of Zn in the mandibles of both species and sexes, suggesting an adaptation to egress from host nests.