The parasitic wasp genus Aphaereta Foerster, 1863, belongs to the large subfamily Alysiinae Leach, 1815 (Hymenoptera: Braconidae) and contains solitary or gregarious endoparasitoids of larvae of cyclorrhaphous Diptera living in decaying organic matter. A new species, Aphaereta vondelparkensis sp. n. (Braconidae, Alysiinae, Alysiini), from a city park in the centre of Amsterdam (Vondelpark) is described and illustrated. The species was discovered on a so-called taxon expedition, in which experts and citizen scientists collaborate on taxonomic projects. The finding highlights the fact that new animal species can still be discovered today, even in the busiest park of the capital of one of the best studied European countries.

Anthropogenic environmental change is leading to changes in distribution for many organisms. While this is frequently discussed for prominent organisms of high conservation value, the same is true for the many cryptic species that rarely figure in debates on the human impact. One such cryptic taxon is the European Ptomaphagus sericatus (Chaudoir, 1845) and related forms. During a citizen science expedition in the Vondelpark, Amsterdam, the Netherlands, we obtained two forms of this species complex. We placed the examination of these specimens in the context of a re-analysis of the species group, and, using DNA barcoding and genital study on material collected thoughout Europe, found that the P. sericatus species complex consists of three distinct, partly sympatric species, one of which was previously undescribed. On the basis of collection data, at least two species, P. medius and P. thebeatles sp. n., show signs of having recently undergone (possibly anthropogenic) range changes, with P. medius even reaching North America. We describe P. thebeatles sp. n.; we raise two subspecies, viz. P. sericatus sericatus (Chaudoir, 1854) and P. sericatus medius (Rey, 1889) to the level of species, and designate a neotype for the former; we identify P. dacicus Jeannel, 1934 and P. pyrenaeus Jeannel, 1934 as junior synonyms of P. sericatus, and P. compressitarsus (Rey, 1889) as a junior synonym of P. subvillosus Goeze, 1777; we identify P. septentrionalis Jeannel, 1934 and P. miser (Rey, 1889) as junior synonyms of P. medius; we designate lectotypes for P. medius and P. miser.