Stylogomphus thongphaphumensis (Odonata: Anisoptera: Gomphidae), a new gomphid dragonfly and the first record of S. malayanus Sasamoto, 2001 from Thailand.

Stylogomphus thongphaphumensis sp. nov. is described from a type series of specimens reared from larvae (holotype ♂, Huai Khayeng, Thong Pha Phum district, Kanchanaburi Province; 14°36'20″N 98°34'38″E, 206 m a.

Description of two final stadium Onychogomphus larvae from Thailand (Odonata: Gomphidae).

The final stadium larvae of Onychogomphus castor Lieftinck and O. duaricus Fraser are described and illustrated for the first time based on reared specimens from Thailand. The taxonomic characteristics of the larvae of the genus Onychogomphus are discussed and summarized.

Description of the last stadium larva and female of Microgomphus thailandica Asahina, 1981 (Odonata: Gomphidae).

The last stadium larva of Microgomphus thailandica is described, illustrated and compared with the larvae of congeneric species based on reared specimens collected from the Phachi headwater stream, Ratchaburi province, Thailand. The female adult of this species is described for the first time from a reared specimen from the same locality.

Description of the final-instar larva of Heliogomphus selysi Fraser (Odonata: Gomphidae).

The final instar larva of Heliogomphus selysi Fraser, 1925, is described and illustrated for the first time based on specimens collected in Ratchaburi province, Thailand. Antennae, legs and paraprocts are similar morphologically to H. kelantanensis and H.