Two new species ofFloresorchestia(Crustacea: Amphipoda) are described from Amphawa Estuary, Samut Songkhram Province, Thailand.Floresorchestia amphawaensissp. nov.is a riparian-hoppers living near agricultural and urban areas, being distinguished by the following character states: left mandible lacinia mobilis 4-dentate; gnathopod 2 palm reaching about 34%; telson as broad as long, with four robust setae per lobe.Floresorchestia pongratisp. nov.are described as riparian-hoppers living in the moist area near Mae Klong canal banks with a unique left mandible lacinia mobilis 5-dentate; gnathopod 2 palm reaching 30% and telson with seven robust setae per lobe. The status and the problem of diagnostic character states of the genusFloresorchestiaare discussed.

Floresorchestia has been recorded from the South African coast throughout the tropical Indo-Pacific and Caribbean seas. Platorchestia exhibits a distribution along the coastlines of the Atlantic Ocean and has been documented in the Baltic and Mediterranean seas, North America, Bermuda, and South Africa; however, it has not been recorded in Southeast Asia. This study presents the discovery of two new species of Floresorchestia and Platorchestia (Crustacea: Amphipoda) from a small creek bank in Trat and Bang Pu, Samut Prakan Province, respectively. These new species, classified as riparian hoppers, significantly contribute to the existing biodiversity in Southeast Asia. Floresorchestia trisetosasp. nov. can be distinguished by left mandible lacinia mobilis 4-dentate; gnathopod 2 palm reaching approximately 34%; telson as broad as long, with three robust setae per lobe. Platorchestia aquaticussp. nov. can be distinguished by gnathopod 1 subchelate, cuspidactylate, gnathopod 2 palm reaching approximately 35%; telson with three marginal robust setae, and three apical robust setae per lobe.

The Eurypalpae genus group includes two genera, Ceratopompa Karsch and Zulpha Walker, which are distributed from southeastern Asia to northern Oceania southwards, and to southern China northwards. Each genus has been recorded as monotypic, including two mysterious taxa: C. festiva Karsch and Z. perlaria (Westwood). In this study, we redescribe the known species with broadened distributional ranges, and describe 2 new species: Zulpha ruohua sp. nov. and Zulpha fenghuang sp. nov., with relevant illustrations. The geographic fistribution of the genus group is discussed and mapped. The types are deposited in Insect Collection of Institute of Zoology, Chinese Academy of Sciences, Beijing, China (IZCAS).

Within the damselfly subfamily Platycnemidinae, eight species are currently recognized in South-East Asia. The final stadium larvae of only three of them have been so far described. The final stadium larva of Copera chantaburii is described and illustrated for the first time, based on reared specimens, and new provincial records both of larvae and adults of C. chantaburii are also provided. The larva of C. chantaburii can be distinguished from known species by the following combination of characters: square or almost horizontal rectangular shape of the outer lobe of the labial palp and fimbriated caudal lamellae that are stout at the base and narrow to an acute tip. The final stadium larva of Pseudocopera ciliata is redescribed with possibly diagnostic characters, such as the shape of the distal margin of the labial palp, the ratio of the length of caudal lamellae length and body length, setae on the margin of caudal lamellae and the setae on the terminal filament of the caudal lamellae.

The orthotyline plant bug genus Zanchius Distant, 1904 is taxonomically reviewed from Vietnam for the first time with the description of a new species, Zanchius tuehang Kim & Jung, sp. nov. Detailed descriptions and diagnoses of the species are provided, along with a key to the Vietnamese Zanchius species, supported by illustrations and photographs. Notes on host sharing, associations with auchenorrhynchan species, and potential distributions are also included.

Lestes decipiens Kirby, 1893 is restored in the species rank upon reconsideration of the structure of its male paraprocts against those of L. dorothea Fraser, 1924 and L. praemorsus Hagen in Selys, 1862 s. str. The two latter names could be synonyms. Lestes praecellens Lieftinck, 1937 could be another synonym, which is a matter of further research. The strong differences between the males of L. dorothea and L. decipiens in the male paraprocts are illustrated and the unfortunate confusion concerning this valuable character in literature is discussed. The differences between females of L. dorothea and L. decipiens are outlined. Lestes dorothea is for the first time reported for the fauna of Cambodia, by a finding of the first author in 2024 and re-identification of a specimen in the collection of 2018 by the second author, both from Mondulkiri Province. Its presence also in Laos is inferred from literature. Potentially undescribed Lestes species were recognised in literature reports.