Spatio-temporal dynamics and diversity of hematophagous flies (Diptera: Muscidae, Tabanidae, and Glossinidae) in livestock areas of Southern Benin: dominance of Stomoxys and occurrence of Glossina tachinoides with implications for vector surveillance.

African animal trypanosomiases (AAT) are vector-borne diseases transmitted by hematophagous flies, causing substantial economic losses in sub-Saharan African livestock systems. No multisite, inter-seasonal entomological study has previously characterized vector communities in southern Benin. This study characterizes their spatio-temporal distribution and diversity to inform AAT surveillance. A multisite survey was conducted across 6 communes during 2 contrasting seasons in 2025, using Vavoua, biconical, and Nzi traps deployed for 72 consecutive hours per session. Flies were identified morphologically, and apparent density per trap per day (ADT) was estimated with 95% confidence intervals. Diversity was assessed via richness, Shannon-Wiener, Simpson, and Pielou indices, and a negative binomial GLM tested effects of commune, season, and their interaction on ADT. Tsetse flies were confirmed by ITS1-PCR. Overall, 6,550 flies from 5 genera and 10 species were collected (ADT = 10.11 [95% CI: 8.53 to 11.73] flies/trap/day). Stomoxys niger dominated (92.5%), followed by Stomoxys calcitrans (4.7%), Chrysops distinctipennis (1.1%), and Tabanus par (1.0%); remaining species each contributed <0.3%. Capture rates differed markedly among trap types (18.5, 9.5, and 1.9 flies/trap/night for Vavoua, Nzi, and biconical traps; P < 0.001). Six Glossina tachinoides were confirmed exclusively in Dogbo. ADT varied significantly by commune, season, and their interaction. Diversity was consistently low (Shannon H' = 0.18 to 0.70), and rarefaction/extrapolation indicated adequate sampling completeness. This first inventory reveals a community strongly dominated by S. niger and supports persistence of a residual tsetse focus in Dogbo. Dangbo, Djidja, and Dogbo emerge as priority surveillance areas, with implications beyond classical tsetse-focused control.