New Records of Scelionidae (Hymenoptera) Egg Parasitoids of Stink Bugs on Soybean and Maize in Tropical Regions

Abstract

Extensive faunistic surveys were conducted in soybean and maize agroecosystems across tropical regions to document the diversity, distribution, and host associations of scelionid egg parasitoids (Hymenoptera: Scelionidae) attacking stink bugs. Field sampling was carried out during different crop growth stages using systematic collection of stink bug egg masses from foliage, followed by laboratory rearing to obtain emerging parasitoids. Adult scelionids were identified based on detailed morphological characteristics, including antennal segmentation, body sculpture, wing venation, and metasomal structure, resulting in the documentation of several species associated with Pentatomidae egg masses. Multiple new distributional records were recorded from soybean and maize ecosystems in the surveyed tropical areas. Molecular identification using mitochondrial cytochrome oxidase I (COI) gene sequencing supported morphological determinations and clarified phylogenetic relationships among closely related taxa. The parasitoids were predominantly associated with egg masses of major stink bug pests infesting soybean and maize, indicating their important role in natural regulation of hemipteran populations. Seasonal abundance patterns showed higher parasitoid emergence during periods of increased stink bug oviposition activity under warm and humid conditions typical of tropical climates. Variations in species composition and parasitism rates were influenced by cropping systems, habitat complexity, and pesticide usage intensity. Fields with reduced insecticide applications and higher plant diversity supported greater scelionid diversity and higher levels of natural parasitism. The discovery of new distributional records expands current knowledge of scelionid biodiversity in tropical agroecosystems and highlights their ecological importance as effective egg parasitoids. Conservation of these beneficial insects through habitat management and reduced chemical inputs can enhance biological control of stink bugs in soybean and maize production systems.