The genus Dettopsomyia was established by Lamb in 1914 for a single species, De. formosa described therein. It contains 13 known species recorded from the Old World (the Oriental, Australasian, Palearctic and Afrotropical regions). In the present paper, five new species discovered from southern China are described as members of Dettopsomyia: De. acutipenis Wang & Gao, sp. nov., De. serripenis Wang & Gao, sp. nov., De. discontinua Wang & Gao, sp. nov., De. camelonota Wang, Li & Gao, sp. nov. and De. paranigrovittata Wang, Li & Gao, sp. nov. The new species were delimitated, based on not only morphological characters but also molecular data.

Based on specimens collected from Yunnan, Xizang, and Taiwan in China, nine new species of the Lordiphosa denticeps species group, L. mikioides sp. nov., L. kimurai sp. nov., L. anthophilia sp. nov., L. yangi sp. nov., L. tibetica sp. nov., L. medogensis sp. nov., L. hamatispina sp. nov., L. secula sp. nov., and L. spatulata sp. nov., were described and four known species, L. denticeps (Okada & Sasakawa), L. neokurokawai (Singh & Gupta), L. ramula Zhang, and L. tripartita (Okada), were redescribed. In addition, we provided a key to all species of this species group. Males of three new species, L. mikioides, L. kimurai, and L. anthophilia, have distinct sex-combs consisting of black, stout teeth on the 1st and 2nd tarsomeres of foreleg; the large, longitudinal sex-comb on the 1st tarsomere is similar to those seen in the L. miki species group and the subgenus Sophophora Sturtevant of the genus Drosophila Fallen. Two of these and another new species were collected at flowering Impatiens L. (Balsaminaceae) stands: all specimens of L. anthophilia and L. medogensis directly from flowers, and some specimens of L. kimurai by net sweeping. The presence of large, longitudinal sex-combs and the flower-visiting habit were reported for the first time in the L. denticeps group.

Species of the genus Colocasiomyia de Meijere feed/breed on inflorescences/infructescences of the plants from the families Araceae, Arecaceae and Magnoliaceae. Although most of them utilize plants from the subfamily Aroideae of Araceae, three species of the recently established C. gigantea species group make use of plants of the subfamily Monsteroideae. We describe four new species of the gigantea group found from Yunnan, China: Colocasiomyia longifilamentata Li & Gao, sp. n., C. longivalva Li & Gao, sp. n., C. hailini Li & Gao, sp. n., and C. yini Li & Gao, sp. n. The species delimitation is proved in virtue of not only morphology but also DNA barcodes, i.e., sequences of the partial mitochondrial COI (cytochrome c oxidase subunit I) gene. Some nucleotide sites with fixed status in the alignment of the COI sequences (658 sites in length) are used as “pure” molecular diagnostic characters to delineate species in the gigantea group.

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.

Breeding habits of essential dependence on flowers for larval food resources have evolved repeatedly in separate lineages of the Drosophilidae. However, flowers of Impatiens L. have never been recognized as hosts for drosophilid flies until recently: two Hirtodrosophila species, H. actinia (Okada) and H. yapingi Gao, were found feeding and breeding on Impatiens flowers. During our recent field surveys in central and southern China, a great number of drosophilid flies morphologically resembling the two species were collected, almost exclusively from flowers of Impatiens (family Balsaminaceae) and the family Gesneriaceae. In the present study, these specimens were identified on the basis of morphological characters and/or partial DNA sequences of the mitochondrial COI (cytochrome c oxidase subunit I gene, used as a barcoding marker). As a result, 39 new species were recognized. We then reconstructed the phylogenetic relationships among most of them, based on concatenated DNA sequences (3047 nucleotide sites) of two mitochondrial (COI and COII, i.e., cytochrome c oxidase subunits I and II, respectively) and three nuclear genes (ATPsyn-alpha, alphaTub84B and Hsc70cb, i.e., ATP synthase alpha, alpha-Tubulin at 84B and Hsc70Cb isoform H, respectively). In the resulting Bayesian and ML (maximum likelihood) trees, three well-supported clades were recognized, with a few species having remained uncertain for their phylogenetic positions. We also conducted a cladistic analysis with data of adult morphological characters to investigate the phylogenetic positions of a few species of which DNA sequence data were not available, and to investigate the classification of species groups with definition of their diagnoses. In consequence, we established a new genus, Impatiophila, for the species visiting flowers of Impatiens and Gesneriaceae, described all the new species, and revised the taxonomy of some known species.