Flies of the Colocasiomyia toshiokai species group depend exclusively on inflorescences/infructescences of the aroid tribe Homalomeneae. The taxonomy and reproductive biology of this group is reviewed on the basis of data and samples collected from Southeast Asia. The species boundaries are determined by combining morphological analyses and molecular species delimitation based on sequences of the mitochondrial COI (cytochrome c oxidase subunit I) gene. For the phylogenetic classification within this species group, a cladistic analysis of all the member species is conducted based on 29 parsimony-informative, morphological characters. As a result, six species are recognised within the toshiokai group, including one new species, viz. C. toshiokai, C. xanthogaster, C. nigricauda, C. erythrocephala, C. heterodonta and C. rostrata sp. n. Various host plants are utilised by these species in different combinations at different localities: Some host plants are monopolized by a single species, while others are shared by two or three species. C. xanthogaster and C. heterodonta cohabit on the same host plant in West Java, breeding on spatially different parts of the spadix. There is a close synchrony between flower-visiting behaviour of flies and flowering events of host plants, which indicate an intimate pollination mutualism.
The annotated chromosome numbers of 25 species from 6 families of monocotyledons, most of them (14) belonging to Poaceae family, are presented here. The data, except three chromosome counts (Allium oleraceum from Hungary and Calamagrostis villosa from Slovakia), are all based on plants collected in the Czech Republic. The karyological data of 21 species represents new information. While the majority of species presented here originated from one or two localities each, the species Calamagrostis villosa has been studied more extensively: all plants, collected altogether at 13 localities (mountain and lower altitudes), are characterized by an invariable decaploid level (2n = 70). The record of triploid Allium oleraceum is only the second reference to this rare ploidy level in this species. All original karyological data are compared with literature references to particular species, preferentially from Europe.