Mangrove forest ecosystem preserves diversity of species, which includes insects. Insects serve as bioindicators, pollinators and nutrient recyclers in the forest. However, the number of insects decline as the forest fades. We conducted this field survey to assess the diversity and abundance of insect species in three selected mangrove swamp forests located in Lagos State, Nigeria. Samples were collected fortnightly using different techniques, for a period of three months. Insects collected were preserved in 70% alcohol, but butterflies and moths were preserved dry.
Representative samples were identified with picture insect mobile application V1.0.8 and confirmed using standard identification keys. Vegetation cover was quite similar in all the areas sampled comprising of Alchornea cordifolia, Eragrosis racemose, Paspalum dilatatum and Avicennia germania. A total of 182 insects were collected belonging to seven Orders, 18 Families and 38 species. The most dominant Order was Coleoptera with relative abundance of 66.48% and the least was Hemiptera (0.59%). The Order Odonata was the most diverse (HꞋ=1.09), and the most dominant species were Pantala flavescens and Sympetrum fonscolombii, having relative abundance of 8.24% each, followed by Palpopleura lucia (7.69%), Ceriagrion glabrum (7.14%) and Lestinogomphus africanus (6.04%). Psedagrion kersteni was rare with relative abundance < 0.5%. Iba site had the highest species diversity (HꞋ=1.24) but lowest number of individuals. This study documents the diversity and abundance of insects in the fast-disappearing mangrove forest of Lagos State, Nigeria.