We present a comprehensive taxonomic revision of the Mecistocephalidae occurring in the Japanese main archipelago and in Taiwan, based on both the critical analysis of published information and the comparative morphological examination of representative specimens, including type material. A total of 34 species in 8 genera are recognised. Diagnostic characters, synonyms and geographical distribution are reviewed and discussed for all species, and a detailed redescription is provided for 12 already known species. An identification key to all species is also provided. The following species are described as new: Arrup ishiianus, Arrup lilliputianus, Arrup longicalix, Arrup kyushuensis, Mecistocephalus changi, Mecistocephalus karasawai. The following synonymies are new: Tygarrup monoporus Shinohara, 1961 = Dicellophilus pulcher (Kishida, 1928); Mecistocephalus fenestratus Verhoeff, 1934 = Mecistocephalus japonicus Meinert, 1886; Mecistocephalus insulomontanus Gressitt, 1941 = Mecistocephalus marmoratus Verhoeff, 1934; Mecistocephalus manazurensis Shinohara, 1961 = Mecistocephalus nannocornis Chamberlin, 1920; Mecistocephalus mirandus Pocock, 1895 = Mecistocephalus japonicus Meinert, 1886; Mecistocephalus okinawaensis Takakuwa, 1939 = Mecistocephalus pauroporus Takakuwa, 1936; Mecistocephalus takakuwai Verhoeff, 1934 = Mecistocephalus diversisternus (Silvestri, 1919). Dicellophilus pulcher (Kishida, 1928) new comb. is here recognised as the valid name for the species previously referred to as Dicellophilus latifrons Takakuwa,1934.

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Gynandromorphs, i.e., individuals with a mix of male and female traits, are common in the wild bees of the genus Megachile (Hymenoptera, Apoidea). We described new transverse gynandromorphs in Megachile pilidens Alfkeen, 1924 and analyze the spatial distribution of body parts with male vs. female phenotype hitherto recorded in the transverse gynandromorphs of the genus Megachile. We identified 10 different arrangements, nine of which are minor variants of a very general pattern, with a combination of male and female traits largely shared by the gynandromorphs recorded in 20 out of 21 Megachile species in our dataset. Based on the recurrence of the same gynandromorph pattern, the current knowledge on sex determination and sex differentiation in the honey bee, and the results of recent gene-knockdown experiments in these insects, we suggest that these composite phenotypes are possibly epigenetic, rather than genetic, mosaics, with individual body parts of either male or female phenotype according to the locally expressed product of the alternative splicing of sex-determining gene transcripts.

An account of the Antonio Giordani Soika Eumeninae collection housed at the Natural History Museum of Venice Giancarlo Ligabue is presented, following its recent reorganization. A list of identified species, with the count of specimens, is provided, as well as details on type specimens. With over 21,000 identified specimens and 2,756 type specimens from all zoogeographical regions, the collection covers over 60% of the world’s Eumeninae species. Several incongruities emerged during the verification of type specimens. A brief history of the collection is presented, with comments on Giordani Soika’s activity.

The Neartic species Acanalonia conica (Say 1830) has been recently found in Italy. Analysis shows that the species has a good capability to settle outside its natural range. A. conica is a very polyphagous species and the population density in Italy appears larger than the one recorded in North America. We conclude that A. conica should be regarded as a potential pest in Europe.