Description of Trypoxylonsicklum sp. nov. from Vietnam and a key to species in the Trypoxylonfulvocollare group (Hymenoptera, Crabronidae).

Background: Trypoxylon Latreille, 1796 (Hymenoptera, Crabronidae) consists of 633 known species worldwide and the genus is divided into numerous species groups. In Vietnam, 19 species of Trypoxylon have been recorded to date. In this study, a new species, Trypoxylonsicklum Pham and Antropov sp. nov. is described and illustrated from Vinh Phuc Province, Vietnam. The new species is the second member of the Trypoxylonfulvocollare species group. A key to species in the Trypoxylonfulvocollaris group is presented. New information: Trypoxylonsicklum Pham and Antropov sp. nov., is described as a new species and is the second member of the Trypoxylonfulvocollare species group. A key to species in the Trypoxylonfulvocollaris group is presented.

New record of the rare genus Analysson Krombein, 1985 (Hymenoptera: Crabronidae) from Vietnam, with description of a new species.

Analysson Krombein 1985, a rare genus of the family Crabronidae, is recorded for the first time from Vietnam. Analysson vietnamensis Pham sp. nov., the second species of the genus, is described and illustrated. A key to both species of Analysson is presented.

Taxonomic studies on Dasyproctus Lepeletier & Brullé (Hymenoptera: Crabronidae) from North Vietnam with description of two new species.

Seven species of Dasyproctus Lepeletier & Brullé, 1835 (Hymenoptera: Crabronidae) are recorded from North Vietnam. Of these, D. vietnamensis and D. longi are new species, and D. idrieus (Cameron) and D. pentheri Leclercq are recorded for the first time from the country. Keys to both sexes of Dasyproctus from North Vietnam based on morphological characters are given, and new distributional records are also presented.

The genus Chalybion Dahlbom, 1843 (Hymenoptera: Sphecidae) from Northwest Vietnam, with description of a new species.

The genus Chalybion Dahlbom, 1843 from northwest Vietnam is studied. Six species of the genus are recorded for the area. Of these, C. dolichothorax (Kohl, 1918) and C. gracile Hensen, 1988 are new records, whereas C. tanvinhensis sp. nov. is described as a new species. Notes on the nest of the new species and keys to both sexes of the six species reported from northwest Vietnam are provided.