If the specimen feeds on seeds then It is an Eurytomidae wasp within the superfamily Chalcidoidea. Unlike most chalcidoids, the larvae of many are phytophagous (feeding in stems, seeds, or galls), while others are more typical parasitoids. I think Umberto is right, it seems a Sycophila sp, but we need the name of the tree ( hostplant) to be sure which species is.
Thank you both Luis Miguel Constantino and Umberto Bernardo for giving me the direction to identify the species. I found the insect from Cordia species. I kept healthy looking seeds, having no hole or crack, washed before incubation and kept in glass bottles for several months. Then, it emerges.
A new species of Eurytoma (Hymenoptera: Eurytomidae) attacking Quadrastichus spp. (Hymenoptera: Eulophidae) galling Erythrina spp. (Fabaceae), with a summary of African Eurytoma biology and species checklist.
Thank you very much for your information. Actually, I had seen the specified insect in the species mentioned in the literature. Unfortunately, there is morphological difference between the two species. Maybe, I need to give you more information.