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The generic taxonomy and host specialization of Xenidae have been understood differently by previous authors. Although the recent generic classification has implied a specialization on the level of host families or subfamilies, the hypothesis that each xenid genus is specialized to a single host genus was also previously postulated. A critical evaluation of the classification of the genera of Xenidae is provided here based on morphology in accordance with results of recent molecular phylogenetic studies. External features of the female cephalothoraces and male cephalothecae were documented in detail with different techniques. Diagnoses and descriptions are presented for all 13 delimited genera. The earliest diverging genera are usually well characterized by unique features, whereas deeply nested genera are usually characterized by combinations of characters. Three new genera are described: Sphecixenos gen. nov. , Tuberoxenos gen. nov. , and Deltoxenos gen. nov. Five previously described genera are removed from synonymy: Tachytixenos Pierce, 1911, stat. res. ; Brasixenos Kogan & Oliveira, 1966, stat. res. ; Leionotoxenos Pierce, 1909, stat. res. ; Eupathocera Pierce, 1908, stat. res. ; and Macroxenos Schultze, 1925, stat. res. One former subgenus is elevated to generic rank: Nipponoxenos Kifune & Maeta, 1975, stat. res. Monobiaphila Pierce, 1909, syn. nov. and Montezumiaphila Brèthes, 1923, syn. nov. are recognized as junior synonyms of Leionotoxenos Pierce, 1909, stat. res. Ophthalmochlus Pierce, 1908, syn. nov. , Homilops Pierce, 1908, syn. nov. , Sceliphronechthrus Pierce, 1909, syn. nov. , and Ophthalmochlus (Isodontiphila) Pierce, 1919, syn. nov. are recognized as junior synonyms of Eupathocera Pierce, 1908, stat. res. A preliminary checklist of 119 described species of Xenidae with information on their hosts and distribution is provided. The following 14 species are recognized as valid and restituted from synonymy: Tachytixenosindicus Pierce, 1911, stat. res. ; Brasixenosacinctus Kogan & Oliveira, 1966, stat. res. ; Brasixenosaraujoi (Oliveira & Kogan, 1962), stat. res. ; Brasixenosbahiensis Kogan & Oliveira, 1966, stat. res. ; Brasixenosbrasiliensis Kogan & Oliveira, 1966, stat. res. ; Brasixenosfluminensis Kogan & Oliveria, 1966, stat. res. ; Brasixenosmyrapetrus Trois, 1988, stat. res. ; Brasixenoszikani Kogan & Oliveira, 1966, stat. res. ; Leionotoxenoshookeri Pierce, 1909, stat. res. ; Leionotoxenosjonesi Pierce, 1909, stat. res. ; Leionotoxenoslouisianae Pierce, 1909, stat. res. ; Eupathoceraluctuosae Pierce, 1911, stat. res. ; Eupathoceralugubris Pierce, 1909, stat. res. ; Macroxenospiercei Schultze, 1925, stat. res. New generic combinations are proposed for 51 species: Leionotoxenosarvensidis (Pierce, 1911), comb. nov. ; Leionotoxenosbishoppi (Pierce, 1909), comb. nov. ; Leionotoxenosforaminati (Pierce, 1911), comb. nov. ; Leionotoxenosfundati (Pierce, 1911), comb. nov. ; Leionotoxenoshuastecae (Székessy, 1965), comb. nov. ; Leionotoxenositatiaiae (Trois, 1984), comb. nov. ; Leionotoxenosneomexicanus (Pierce, 1919), comb. nov. ; Leionotoxenosprolificum (Teson & Remes Lenicov, 1979), comb. nov. ; Leionotoxenosrobertsoni (Pierce, 1911), comb. nov. ; Leionotoxenostigridis (Pierce, 1911), comb. nov. ; Leionotoxenosvigili (Brèthes, 1923), comb. nov. ; Eupathoceraargentina (Brèthes, 1923), comb. nov. ; Eupathoceraauripedis (Pierce, 1911), comb. nov. ; Eupathocerabucki (Trois, 1984), comb. nov. ; Eupathoceraduryi (Pierce, 1909), comb. nov. ; Eupathoceraerynnidis (Pierce, 1911), comb. nov. ; Eupathocerafasciati (Pierce, 1909), comb. nov. ; Eupathocerafuliginosi (Brèthes, 1923), comb. nov. ; Eupathocerainclusa (Oliveira & Kogan, 1963), comb. nov. ; Eupathocerainsularis (Kifune, 1983), comb. nov. ; Eupathoceramendozae (Brèthes, 1923), comb. nov. ; Eupathocerapiercei (Brèthes, 1923), comb. nov. ; Eupathocerastriati (Brèthes, 1923), comb. nov. ; Eupathocerataschenbergi (Brèthes, 1923), comb. nov. ; Eupathocerawestwoodii (Templeton, 1841), comb. nov. ; Macroxenospapuanus (Székessy, 1956), comb. nov. ; Sphecixenosabbotti (Pierce, 1909), comb. nov. ; Sphecixenosastrolabensis (Székessy, 1956), comb. nov. ; Sphecixenosdorae (Luna de Carvalho, 1956), comb. nov. ; Sphecixenoserimae (Székessy, 1956), comb. nov. ; Sphecixenosesakii (Hirashima & Kifune, 1962), comb. nov. ; Sphecixenosgigas (Pasteels, 1950), comb. nov. ; Sphecixenoskurosawai (Kifune, 1984), comb. nov. ; Sphecixenoslaetum (Ogloblin, 1926), comb. nov. ; Sphecixenosorientalis (Kifune, 1985), comb. nov. ; Sphecixenosreticulatus (Luna de Carvalho, 1972), comb. nov. ; Sphecixenossimplex (Székessy, 1956), comb. nov. ; Sphecixenosvanderiisti (Pasteels, 1952), comb. nov. ; Tuberoxenosaltozambeziensis (Luna de Carvalho, 1959), comb. nov. ; Tuberoxenossinuatus (Pasteels, 1956), comb. nov. ; Tuberoxenossphecidarum (Siebold, 1839), comb. nov. ; Tuberoxenosteres (Pasteels, 1950), comb. nov. ; Tuberoxenostibetanus (Yang, 1981), comb. nov. ; Deltoxenosbequaerti (Luna de Carvalho, 1956), comb. nov. ; Deltoxenosbidentatus (Pasteels, 1950), comb. nov. ; Deltoxenoshirokoae (Kifune & Yamane, 1992), comb. nov. ; Deltoxenosiwatai (Esaki, 1931), comb. nov. ; Deltoxenoslusitanicus (Luna de Carvalho, 1960), comb. nov. ; Deltoxenosminor (Kifune & Maeta, 1978), comb. nov. ; Deltoxenosrueppelli (Kinzelbach, 1971a), comb. nov. ; Xenosropalidiae (Kinzelbach, 1975), comb. nov. Xenosminor Kinzelbach, 1971a, syn. nov. is recognized as a junior synonym of X.vesparum Rossi, 1793. Ophthalmochlusduryi Pierce, 1908, nomen nudum and Eupathoceralugubris Pierce, 1908, nomen nudum are recognized as nomina nuda and therefore unavailable in zoological nomenclature. The species diversity of Xenidae probably remains poorly known: the expected number of species is at least twice as high as the number presently described., (Daniel Benda, Hans Pohl, Yuta Nakase, Rolf Beutel, Jakub Straka.)

Parasites sometimes manipulate their host's behavior to increase their own fitness by enhancing the likelihood that their offspring will reach their hosts. Bees are often parasitized by immobile adult female strepsipterans which seem to modify bees' behavior to facilitate the release of mobile first-instar larvae onto flowers. To better understand how the parasite may modify the host's behavior, we compared the foraging behavior of the sweat bee Lasioglossum apristum (Vachal, 1903) (Hymenoptera: Halictidae) between bees parasitized and unparasitized by the strepsipteran Halictoxenos borealis Kifune, 1982 (Strepsiptera: Stylopidae). Both parasitized and unparasitized bees frequently visited Hydrangea serrata (Thunb.) (Cornales: Hydrangeaceae) inflorescences, which are polleniferous but nectarless. On H. serrata inflorescences, unparasitized bees collected pollen from the anthers, but parasitized bees did not collect or eat pollen. Instead, they displayed a peculiar behavior, bending their abdomens downward and pressing them against the flower. This peculiar behavior, which was observed only in bees parasitized by a female strepsipteran in the larvae-releasing stage, may promote the release of mobile first-instar larvae onto flowers. Our observations suggest that the altered flower-visiting behavior of parasitized bees may benefit the parasite. Moreover, it suggests that strepsipteran parasites may modify their host's behavior only when the larvae reach a certain life stage., (© The Author(s) 2021. Published by Oxford University Press on behalf of Entomological Society of America.)

Background: Geographic differences in floral size sometimes reflect geographic differences in pollinator size. However, we know little about whether this floral size specialization to the regional pollinator size occurred independently at many places or occurred once and then spread across the distribution range of the plant species., Results: We investigated the relationship between the local floral size of flowers and local pollinator size in 12 populations of Lamium album var. barbatum on two different mountains in the Japan Alps. Then, using 10 microsatellite markers, we analyzed genetic differentiation among the 12 populations. The results showed that local floral size was correlated with the average size of relevant morphological traits of the local pollinators: floral size was greater in populations visited frequently by the largest flower visitors, Bombus consobrinus queens, than it was in other populations. We also found that the degree of genetic similarity between populations more closely reflected interpopulation geographic proximity than interpopulation similarity in floral size., Conclusions: Although genetic similarity of populations was highly associated with geographic proximity, floral size varied independently of geographic proximity and was associated with local pollinator size. These results suggest that in L. album var. barbatum, large floral size evolved independently in populations on different mountains as a convergent adaptation to locally abundant large bumblebee species.

The parasitoid wasp Protaphidius nawaii parasitizes the aphid Stomaphis japonica , which is obligatorily attended by several species of ants of genus Lasius . Subgenus Lasius or Dendrolasius ants use different defense strategies to protect the aphids that they attend ( Lasius , shelter building; Dendrolasius , aggressive attack). We performed molecular phylogenetic analysis based on partial mitochondrial DNA sequences of P. nawaii and found that the parasitoid wasp consists of two highly differentiated genetic lineages. Although these two lineages distributed sympatrically, one tends to parasitize aphids attended by ants of subgenus Lasius , and the other parasitizes aphids attended by ants of subgenus Dendrolasius . The two lineages of P. nawaii appear to exhibit different oviposition behaviors adapted to the different aphid-protection strategies of the two ant subgenera.

After the break-up of Gondwana dispersal of organisms between America, Australia and Africa became more complicated. One of the possible remaining paths led through Antarctica, that was not yet glaciated and it remained habitable for many organisms. This favourable climate made Antarctica an important migration corridor for organisms with good dispersal ability, such as Aculeata (Hymenoptera), till the Oligocene cooling. Here we tested how cooling of Antarctica impacted global dispersal of Aculeata parasites (Strepsiptera: Xenidae). Our data set comprising six nuclear genes from a broad sample of Xenidae. Bayesian dating was used to estimate divergence times in phylogenetic reconstruction. Biogeography was investigated using event-based analytical methods: likelihood-based dispersal-extinction-cladogenesis and Bayesian models. The Bayesian model was used for reconstruction of ancestral host groups. Biogeographical methods indicate that multiple lineages were exchanged between the New World and the Old World + Australia until the Antarctica became completely frozen over. During the late Paleogene and Neogene periods, several lineages spread from the Afrotropics to other Old World regions and Australia. The original hosts of Xenidae were most likely social wasps. Within one lineage of solitary wasp parasites, parallel switch to digger wasps (Sphecidae) occurred independently in the New World and Old World regions. The biogeography and macroevolutionary history of Xenidae can be explained by the combination of dispersal, lineage extinction and climatic changes during the Cenozoic era. A habitable Antarctica and the presence of now-submerged islands and plateaus that acted as a connection between the New World and Old World + Australia provided the possibility for biotic exchanges of parasites along with their hymenopteran hosts. Although Xenidae are generally host specialists, there were significant host switches to unrelated but ecologically similar hosts during their evolution. There is little or no evidence for cophylogeny between strepsipteran parasites and hymenopteran lineages., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Xenos is a strepsipteran genus whose members are parasitic to eusocial wasps, including the hornet genus Vespa. We undertook an extensive sampling of strepsipterans in Xenos from hornets collected in East Asia and performed molecular phylogenetic analyses based on mitochondrial cytochrome c oxidase subunit I gene sequences (652 bp) to investigate the cryptic diversity among 21 individuals of strepsipterans. The analyses, accompanied by morphological examination, revealed that these strepsipterans represent two distinct species, X. moutoni du Buysson, 1903 and X. oxyodontes sp. nov. The two species differed in their host-utilization pattern: the latter was almost specific to Vespa analis and V. simillima, whereas the former was associated with other species in Vespa.