OWOSANNI ESTHER OREOFE

Mosquitoes are common insect pests and are well known as major vectors responsible for transmitting important parasitic and arboviral diseases such as malaria, filariasis, dengue fever, chikungunya and Zika virus, which pose significant health risks to humans and animals. This study investigated the species composition, sex ratio and distribution of outdoor-resting mosquitoes on the Ugbowo Campus of the University of Benin, Nigeria. Adult mosquitoes were sampled using sweep nets across 14 selected outdoor sites between 3:00 p.m. and 6:00 p.m. from August to September 2025. Identification was carried out using standard morphological keys. A total of 244 adult mosquitoes were recorded, representing seven species: Aedes albopictus (67.6%), Aedes infirmatus (2.87%), Aedes cretinus (0.4%), Aedes vexans (2.87%), Culex quinquefasciatus (25.4%), Coquillettidia fraseri (0.4%) and Mansonia sp. (0.4%). Aedes albopictus was the most abundant (67.6%) and the most widely distributed, occurring in all sampled locations except the Junior Staff Quarters farmland. Aedes cretinus, Coquillettidia fraseri and Mansonia sp. were the least represented, each accounting for 0.4%. The sex ratio showed a higher proportion of females (63.9%) than males (36.1%). The Junior Staff Quarters farmland had the highest mosquito abundance (17.6%), followed by the Faculty of Agriculture (11.5%) and the Ekosodin back gate (11.0%), while Hall 6 recorded the lowest abundance (2.5%). Species diversity was highest at the Faculty of Engineering, Basic Medical Sciences, and Hall 6, whereas the Department of Health Services and the Junior Staff Quarters plantain farm showed the lowest diversity.