Freshwater mussels belonging to the tribe Pseudodontini (Bivalvia: Unionidae: Gonideinae) play a keystone role in riverine and lacustrine environments throughout Southeast Asia. Many of them are narrowly endemic and habitat specialists, which need special conservation efforts. Unfortunately, the systematics of this group is rather poorly understood. Here, we show that Pseudodon inoscularis, the type species of the genus Pseudodon, belongs to the eastern clade of the tribe (Southeast Asia, east of the Salween Basin), and, more certainly, clusters with members of the genus Monodontina. Hence, the latter genus becomes a synonym of Pseudodon, while the subtribe Pseudodontina (=Pilsbryoconchina syn. nov.) should be used as a name for the eastern clade. In turn, the genus Indopseudodon stat. rev. and the subtribe Indopseudodontina subtr. nov. must be applied as valid names for the western clade of the Pseudodontini (Ayeyarwady to Salween). We present a revision of the genus Indopseudodon with an updated synonymy and a description of a new species, I. indawgyiensis sp. nov. We also link four species-level genetic lineages from the Mekong to available taxonomic names in the genera Pseudodon and Sundadontina (Pseudodon cambodjensis, P. vagulus, Sundadontina harmandi, and S. sulcata). Based on morphological features, we revise the taxonomic position of several recent and fossil species that were traditionally placed in the Pseudodontini and transfer them to the genera Parvasolenaia, Pseudodontopsis, Ptychorhynchus, Simpsonasus nom. nov. (a new name for Nasus Simpson, 1900) (Gonideinae: Gonideini), Pseudobaphia (Unioninae: Unionini), Balwantia and Lamellidens (Parreysiinae: Lamellidentini).

The flat-back millipede genus Touranella Attems, 1937 is currently comprised of 13 species, including three new ones from Laos: T. chenla Likhitrakarn, sp. nov., T. srisonchaii Likhitrakarn, sp. nov., and T. jaegeri Likhitrakarn, sp. nov. The generic diagnosis is updated, a key is given to all known species, and their distributions are mapped. Additionally, T. gracilis, the type species of Touranella from Vietnam, has been redescribed and illustrated based on type specimens.

A new species of Southeast Asian dwarf tarantula, Phlogiellus khampheng Sriranan, Songsangchote & Chomphuphuang, sp. nov., is described from Pakse, Champasack Province, Lao PDR. The species is placed within the Yamia group of the genus Phlogiellus, which is characterized by the absence of maxillary lyra. Phlogiellus khampheng Sriranan, Songsangchote & Chomphuphuang, sp. nov. can be distinguished from other species within the Yamia group by the unique morphology of the female spermathecae and the male embolus. The habitat and natural history of P. khampheng Sriranan, Songsangchote & Chomphuphuang, sp. nov. are also discussed, with specimens found in mixed deciduous forests near Pakse, Lao PDR, inhabiting various microhabitats such as soil walls, under rocks, and within tree hollows. An updated comparison of scopula characteristics and labial cuspule counts across Phlogiellus species highlights the variability of these traits and their limitations as diagnostic features. Molecular phylogenetic analyses and species delimitation methods (ABGD and ASAP) further support the recognition of P. khampheng Sriranan, Songsangchote & Chomphuphuang, sp. nov. as a distinct species.

Three new earthworms of the Amynthas corticis-group (Clitellata: Megascolecidae) from Phouleoi Mountain, Lao PDR. Earthworm specimens were collected from Mt. Phouleoi, Viengthong District, Houaphanh Province, Lao PDR. The species belong to the pheretimoid earthworms. All three holandric species key out to the A. corticis-group in Sims & Easton (1972), having spermathecal pores in 5/6–8/9. The new species are: Amynthas ammalinei sp. nov., Amynthas xayi sp. nov., and Amynthas piyakarnae sp. nov. Amynthas ammalinei sp. nov. has male pores superficial on small round porophores, 0.16–0.31 circumference apart. Amynthas xayi sp. nov. has male pores superficial in XVIII at centers of round porophores, 0.17–0.29 circumference apart. Amynthas piyakarnae sp. nov. has male pores superficial on transverse elevated elongate oval pads equatorial on XVIII, pads surrounded by 3–4 small outer rings, 0.25–0.31 circumference apart.

Genetic diversity and ecology are two important aspects of vector species crucial to a full understanding of disease epidemiology. In this study, we examined genetic diversity, genetic structure and the physiochemical parameters of the breeding habitats of the two significant black fly vector species, Simulium chumpornense Takaoka and Kuvangkadilok and S. nodosum Puri, from Laos. Genetic diversity of S. chumpornense in Laos was relatively high with maximum genetic divergence of 3.05% but no significant genetic differentiation between populations. Comparisons with conspecific populations from Thailand also found no genetic differentiation between the two countries. This possibly related to the recent history of this species, as a very recent (31,000 years ago) historical population expansion was detected. Physicochemical parameters of the breeding habitats suggest the ability to utilize diverse stream sizes from small flows (1 m wide) to huge rivers (290 m or more wide). Populations of S. nodosum from Laos had low genetic diversity with maximum genetic divergence of 2.56% and no genetic structuring among populations. Comparisons with those reported from other countries revealed five genetically divergent lineages (I–V) with minimum genetic divergence of 1.36%. The majority (42 of 52) of specimens from Laos belonged to lineage I and the remaining (10) comprised lineage II. Lineage I is the largest and representative of specimens from Thailand, Myanmar, Vietnam, Taiwan and Laos. Population history analysis revealed that lineage I had undergone recent demographic expansion dating back to 7000 years ago. This very recent population expansion resembles others reported from Thailand and possibly indicates a response to increasing human and domestic animals following the agricultural revolution. Breeding sites of S. nodosum are diverse in respect to elevation, velocity, water conductivity and streambed particle size. The ability to utilize a wide variety of breeding sites could promote the production of a large adult population, which can be a pest for humans and other animals.

Adult black flies were collected from diverse habitats in five provinces of Laos. In total, 4659 adults (4570 females and 89 males) were collected. Morphological identification, supplemented with the mitochondrial cytochrome c oxidase I gene, revealed 12 species. The most abundant taxa were Simulium khelangense/S. chumpornense and S. asakoae/S. myanmarense with 58% (2628 of 4476) and 38% (1720 of 4476) of the total specimens, respectively. Simulium asakoae/S. myanmarense was the most geographically widespread taxon (65% of sites) from 174 to 1219 m above sea level. The remaining species were far less abundant (<2%) and found in only one or a few locations. Molecular identifications of vertebrate blood meals indicated that most hosts (57 of 66) were chickens. Five taxa, S. asakoae, S. khelangense, S. myanmarense, S. aureohirtum, and S. striatum group, fed on chickens, representing the first hosts records for the latter three taxa. Simulium daoense fed on water buffalo, marking the first record of this species in Laos and the first report of its blood hosts. The abundance and frequent use of domestic chickens as hosts suggests that S. khelangense and S. asakoae could be significant pests and might serve as vectors of avian blood parasites in Laos.