The purpose of the study is to clarify the diversity and biological characteristics of solitary wasps in the Northeast region of Vietnam. Specific goals of the topic:
- Determining the composition of solitary wasps belonging to the subfamily Eumeninae in the study area.
- Determination of some biological and ecological characteristics of solitary wasps belonging to the subfamily Eumeninae recorded in the study area.

- A total of 23 species in 16 genera have been recorded in the study areas, of which a new species, Pararrhynchium simsanum Nguyen & Tran, 2021, has been described.
- Three types of nests including “burrowers” (3 species), “builders” (6 species), and “renters” (6 species) were collected. The detailed structure of the nests of 13 species was determined.
- The development of those species has 5 stages: egg, larva, pre-pupa, pupa, and adult, recording morphological characteristics and duration of each development phase.
- Their prey is caterpillars. The number and phenotype of prey in each provisioned cell were determined.
- Their natural enemies were 9 species, belonging to 6 families of 3 orders.
- Two common species, Pareumenes quadrispinosus and Rhynchium brunneum, were identified as natural enemies of pest insects.

- One new species was discovered and described.
- A collection of more 150 species of solitary wasps and their natural enemies was built up for futher research.
- Biological and ecological characteristics of some species of solitary wasps were discovered.

- Scientific papers in referred journals (list):
1. Hoa T. Dang, Alexander V. Fateryga, 2021. Nesting biology of Pareumenes quadrispinosus (de Saussure, 1855) (Hymenoptera: Vespidae: Eumeninae) in trap nests in North Vietnam. Journal of Asia-Pacific Entomology, 24 (2021): 1275-1285.  
2. Lien Thi Phuong Nguyen, Ngat Thi Tran, Dien Trong Bui & Toshko Ljubomirov, 2021. Contribution to the genus Pararrhynchiumde Saussure (Hymenoptera: Vespidae: Eumeninae), with description of two new species from Vietnam. Zootaxa 5082 (2): 159-168.
- Specimen collection:  more 150 species of solitary wasps and their natural enemies.