First descriptions of the final stadium larva of Heliogomphus chaoi Karube, 2004 and the adult female of Microgomphus jurzitzai Karube, 2000 from Vietnam (Odonata: Gomphidae).

The larva of Heliogomphus chaoi Karube, 2004 and the adult female of Microgomphus jurzitzai Karube, 2000 are described from Vietnam for the first time. The morphological difference between the larvae of the genera Heliogomphus Laidlaw, 1922 and Microgomphus Selys, 1858 are discussed, which throws doubts about the current taxonomic status of H. retroflexus (Ris, 1912).

Description of Protosticta samtsensis sp. nov. (Odonata: Zygoptera: Platystictidae) from Samtse district, Bhutan.

Protosticta samtsensis sp. nov. (holotype : Bhutan, Samtse District, Norgaygang gewog (Bara), 27.142670N, 88.835228E; altitude 1,264 m, 12-viii-2022), is described from a holotype male and a female paratype and compared with P. himalaica Laidlaw, 1917.

Description of the larva of Indocnemis orang (Frster in Laidlaw, 1907) (Odonata: Platycnemididae: Calicnemiinae) from Thailand, with larval key to the known genera of the family Platycnemididae in Asia.

The larval characters of the genus Indocnemis Laidlaw, 1917 are described based on larval specimens of I. orang (Frster in Laidlaw, 1907) from Thailand. The larvae are characterized by 56 pairs of premental setae, 89 palpal setae of the same length, and vertical lamella caudal gills. The habitats and new provincial records of I. orang in Thailand are also provided in addition to a key to the genera of the family Platycnemididae in Asia.

A review of the Drepanosticta carmichaeli-group, with the description of D. wildermuthi sp. nov. from the Central Highlands of Vietnam (Odonata: Zygoptera: Platystictidae).

A modified and expanded definition of the Drepanosticta carmichaeli-group is given. This includes the species: D. annandalei Fraser, 1924, D. brownelli Tinkham, 1938, D. carmichaeli (Laidlaw, 1915), D. emtrai Dow, Kompier Phan, 2018, D. hongkongensis Wilson, 1997, D. jurzitzai Hmlinen, 1999, D. sumatrana Sasamoto Karube, 2007, D. tenella Lieftinck, 1935, D. vietnamica Asahina, 1997 and D. wildermuthi sp. nov.). The species of the group are reviewed and in most cases illustrated, diagnostic notes are given wherever possible. Drepanosticta polychromatica Fraser, 1931 is considered to be a junior synonym of D. carmichaeli and variation in D. carmichaeli is discussed. Drepanosticta wildermuthi sp. nov. from the Central Highlands of Vietnam (holotype male from Bao Loc district, Lam Dong Province) is described. The female of D. jurzitzai Hmlinen, 1999 is described for the first time. A key to the males of the Drepanosticta carmichaeli-group is provided.

The genus Planaeschna McLachlan, 1895 and its subgroupings in Vietnam, with descriptions of three new species (Odonata: Aeshnidae).

Twelve Planaeschna McLachlan, 1895 species recorded in Vietnam are presented and their subgroupings based on nuclear DNA analysis are discussed. Three new species are described (Planaeschna crux sp. nov. [holotype: Pia Oac NP, Cao Bang Prov.], Planaeschna samurai sp. nov. [holotype: Khau Pha, Tu Le, Yen Bai Prov.] and Planaeschna tsuchi sp. nov. [holotype: Xuan Son NP, Phu Tho Prov.]. Planaeschna celia Wilson Reels, 2001 is recorded from Vietnam for the first time. Planaeschna guentherpetersi Sasamoto, Do Vu, 2013 is shown to be a subspecies of Planaeschna ishigakiana Asahina, 1951. The female of Planaeschna cucphuongensis Karube, 1999 is described for the first time. Additional records are provided for Planaeschna asahinai Karube, 2011, Planaeschna tamdaoensis Asahina, 1996, Planaeschna tomokunii Asahina, 1996, and Planaeschna viridis Karube, 2004. Lastly, the females of two unidentified Planaeschna spp. are illustrated. Information on the ecology of all species is provided.

Description of Chlorogomphus danhkyi sp. nov. from Vu Quang National Park, central Vietnam with notes on other congeners from the Park (Odonata: Chlorogomphidae).

Chlorogomphus danhkyi sp. nov. (Holotype ♂: Khe Ro, Vu Quang National Park, Ha Tinh Province, 15.0444 N, 107.9270 E, altitude 1480 m) based on both sexes is described. The new species differs from Chlorogomphus piaoacensis Karube, 2013 mainly by the shape of male cerci. Other species of Chlorogomphus Selys, 1854 from Vu Quang National Park are also recorded.

A new hopane derivative from the lichen Dirinaria applanata.

Chemical investigation of the lichen Dirinaria applanata led to isolate nine compounds including a new hopane derivative, 1ß-acetoxy-21α-hopane-3ß,22-diol (1) together with six phenolic compounds naming divaricatinic acid (2), methyl divaricatinate (3), methyl-ß-orcinolcarboxylate (4), methyl haematommate (5), divarinol (6), ramalinic acid A (7), and two xanthones namely lichenxanthone (8), 4,5-dichlorolichenxanthone (9). Their structures were elucidated by spectroscopic data in combination with published literature. Except compound 2, all compounds were isolated from this species for the first time.

Description of Coeliccia lephuocdieui sp. nov. from the Central Highlands of Vietnam (Odonata: Zygoptera: Platycnemididae) with notes on its congeners.

Coeliccia lephuocdieui sp. nov. (holotype ♂, 14.2586N, 108.3786E, Kon Ka Kinh National Park in Ayun Commune, Mang Yang District, Gia Lai Province, the Central Highlands of Vietnam) is described and illustrated for both sexes. A comparison of the new species with Coeliccia scutellum Laidlaw, 1932 and C. yamasakii Asahina, 1984 is provided with notes on the morphological variation of the Vietnamese C. scutellum. The female of C. yamasakii is described for the first time.

Protosticta joepani sp. nov. from Borneo with notes on P. kinabaluensis Laidlaw, 1915 (Odonata: Zygoptera: Platystictidae).

Protosticta joepani sp. nov. is described from Malaysian Borneo (holotype male Bario, Kelabit Highlands, Miri Division, Sarawak, Malaysia, deposited in the Naturalis Biodiversity Center, Leiden). It is the sister species of P. kinabaluensis Laidlaw, 1915; some descriptive notes and a set of illustrations are provided of the latter species. A COI gene tree for both species is provided. The placement of both P. joepani and P. kinabaluensis is discussed, but although it is very unlikely that they belong in Protosticta sensu stricto, the issue is left open here.

Description of Coeliccia natgeo sp. nov. from Central Vietnam with keys to the males and females of the hayashii-group (Odonata: Zygoptera: Platycnemididae).

Coeliccia natgeo sp. nov. is described from central Vietnam (holotype ♂, 18.2708 N, 105.3431 E, Khe Nhop, Vu Quang National Park, Ha Tinh Province, deposited in the Zoological Collection of Duy Tan University, Da Nang City, Vietnam). The new species differs from other members of the hayashii-group by males lacking antehumeral stripes, spots and pruinosity on the synthorax and female having the central part of the posterior pronotal lobe reduced to a small projection. Keys to the males and females of the hayashii-group are provided.

First record of Indolestes cyaneus (Selys, 1862) from Vietnam and notes on its color variation (Odonata: Zygoptera: Lestidae).

First record of Indolestes cyaneus (Selys, 1862) from Vietnam with providing illustrations of its detailed structures, as well as notes on the coloration of the populations from Taiwan, Nepal and India.

Coeliccia lecongcoi sp. nov., a new damselfly from the Central Highlands of Vietnam (Odonata: Zygoptera: Platycnemididae).

Coeliccia lecongcoi sp. nov. (holotype ♂, 15.147 N, 107.752 E, Ngoc Linh Nature Reserve, Kon Tum Province, the Vietnamese Central Highlands) is described and illustrated from both sexes. The new species is allied to Coeliccia duytan Phan, 2017 and Coeliccia hayashii Phan Kompier, 2016 but differs by the synthoracic pattern and structure of the appendages and genital ligula of the male and the posterior pronotal lobe of the prothorax of the female.

A synopsis of the Euphaeidae (Odonata: Zygoptera) of Vietnam, with descriptions of two new species of Euphaea.

23 species of Euphaeidae (Odonata: Zygoptera) are reported from Vietnam including two new species of Euphaea, E. saola Phan Hayashi, sp. nov. and E. sanguinea Kompier Hayashi, sp. nov., and four species not recorded previously, Bayadera continentalis Asahina, 1973, B. hyalina Selys, 1879, B. nephelopennis Davies Yang, 1996 and Euphaea pahyapi Hämäläinen, 1985. The females of Anisopleura bipugio Hämäläinen Karube, 2013, Bayadera serrata Davies Yang, 1996 and Euphaea hirta Hämäläinen Karube, 2001 are described for the first time. The mutual taxonomic status of Bayadera hyalina and B. strigata Davies Yang, 1996 is discussed. Distribution maps of all known Vietnamese species, with detailed distribution records, are provided.

Drepanosticta emtrai sp. nov. from Vietnam with a discussion of Drepanosticta vietnamica Asahina, 1997 (Odonata: Zygoptera: Platystictidae).

Drepanosticta emtrai sp. nov. is described from Vietnam (holotype male Ha Tinh Province, 9 vi 2015, to be deposited in RMNH). The new species is allied to D. carmichaeli (Laidlaw, 1915) and a number of other species of Drepanosticta including D. vietnamica Asahina, 1997. New illustrations of the paratype of D. vietnamica are provided and the species is discussed. The Drepanosticta carmichaeli-group, to which the above mentioned species belong, is defined and discussed.

Notes on the genus Indocnemis Laidlaw, 1917 in Vietnam with description of Indocnemismarijanmatoki sp. n. (Odonata, Zygoptera, Platycnemididae).

Indocnemismarijanmatoki sp. n. (holotype ♂, 12°07'10.0"N, 108°5'51.0"E, 1503 m a.s.l., Hon Ba Nature Reserve, Nha Trang city, Khanh Hoa Province, central Vietnam) is described based on both sexes. The morphological variation of Indocnemisorang (Förster in Laidlaw, 1907) is discussed and its distribution in Vietnam updated.

Description of Coeliccia bhriulieci sp. nov. (Odonata: Zygoptera: Platycnemididae) from central Vietnam.

Coeliccia bhriulieci sp. nov. (holotype male from Tay Giang district, Quang Nam province, central Vietnam, deposited in the Zoological collection of the Southern Institute of Ecology, Vietnam Academy of Science and Technology, Ho Chi Minh City, Vietnam) is described based on male specimens. The new species is easily distinguished from other Coeliccia species in the Southeast Asian region by the combination of its blue abdominal tip, black anal appendages and structure of genital ligula with two long flagella extending from lateral corners of apical segment.

Coeliccia mientrung spec. nov. from Central Vietnam (Odonata: Platycnemididae).

Coeliccia mientrung spec. nov. is described from central Vietnam. Detailed differences from the very similar C. pyriformis Laidlaw, 1932, are provided. The female of C. pyriformis is described for the first time.

Description of two new Calicnemia from Vietnam and central Laos with notes on their congeners in Vietnam (Odonata: Platycnemididae).

Descriptions are given of two new species of Calicnemia: C. akahara sp. nov. from central and southern Vietnam and C. hamata sp. nov. from central Laos. C. soccifera Yu & Chen, 2013, and C. haksik Wilson & Reels, 2003, are recorded for the first time from Vietnam; C. uenoi Asahina, 1997, is redescribed with new illustrations provided of its anal appendages and genital ligula; and the occurrence of C. mortoni (Laidlaw, 1917) in Vietnam is discussed.

Description of two new species of Coeliccia from Vietnam (Odonata: Platycnemididae).

Coeliccia hayashii sp. nov. (holotype male, from Doi waterfall, KaNat, K'Bang district, Gia Lai Province, central Vietnam, deposited in VNMN) and Coeliccia mattii sp. nov. (holotype male and female allotype, from Doi Cao, Loc Tan, Bao Lam district, Lam Dong Province, southern Vietnam, deposited in VNMN) are described. The males of both species are characterized by extensive pruinosity on the thorax.