ECOLOGICAL STUDIES ON SIMULID FLIES (DIPTERA: SIMULIIDAE) IN A FAST-FLOWING RIVER ALONG LAJE ROAD, ONDO CITY, ONDO STATE, NIGERIA
DOI:
https://doi.org/10.33003/fjs-2026-1004-4708Keywords:
Simuliidae, blackfly ecology, onchocerciasis, larval/pupal biometry, seasonal abundanceAbstract
Simuliid flies (blackflies) of the family Simuliidae are ecologically and epidemiologically significant in as obligate vectors of Onchocerca volvulus, responsible for onchocerciasis. Their breeding habitats, seasonal abundance, biting activity, and developmental characteristics is essential for assessing transmission risk and improving vector surveillance. Despite onchocerciasis endemicity in Ondo State, ecological documentation of simuliid populations in specific river systems within Ondo City remains limited. This study investigated the ecological characteristics of simuliid flies along a river on Laje Road, Ondo City. Field sampling was conducted at three sites along a fast-flowing river section during the late rainy season (June–August 2024) and early dry season (October–November 2024). Water depth ranged from 16.5–59.0 cm and velocity averaged 0.8 m/s at the fastest site. Overall seasonal mean air temperatures were 27.1°C (rainy season) and 29.9°C (dry season onset) while water temperature exhibited considerably narrower variation, ranging only from 25.2°C to 27.2°C. The narrow thermal range falls within the optimal developmental range (20-28°C) for Simulium damnosum. A total of 55 adult flies were captured, with peak abundance in June and July, and peak biting activity between 1400 and 1700 hours. Adult morphometric measurements showed wing length (mean 8.41 ± 0.47 mm). Thorax length (mean 5.62 ± 0.48 mm); thorax depth (mean 5.28 ± 0.56 mm). Head length (mean 4.04 ± 0.51 mm) and leg length (mean 8.50 ± 0.59 mm). Dimensions are consistent with reference measurements for female S. damnosum. These findings confirm the river as an active simuliid breeding and biting habitat.
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