Seasonal variation of butterflies from high altitude Rugezi marshland, Northern Rwanda

The marshlands provide water resources and support economic, ecological, and human well-being. However, less is known about the biodiversity of insects, particularly butterflies in marshlands of Rwanda. This study was interested with the assessment of species richness and species diversity of butterflies from a high altitude Rugezi marshland. Data were collected twice in 2023 during the dry (June-July) and the rainy (November-December) seasons. The northeast, central and northwest regions of the marshland were demarcated using published geodata and shapefiles of Rugezi, while the opportunistic sampling was used to select the sites with high probability to find butterflies. Within each site, butterflies were systematically sampled using fruit-baited traps made of banana and pineapple and hand sweep netting. Three traps were placed at each sampling point across a transect of 500 m, where 100 m were maintained between two traps. We left traps in the field and collected them after 24 h. Additionally, specimens were collected using the hand sweep net at each sampling point. The collected specimens were stored in glassine envelopes, brought to the entomology laboratory, and identified to family, genus, and species levels using dichotomous keys. The results revealed a total of 75 species classified into 4 families. The Nymphalidae family had more species than Pieridae, Lycaenidae, and Hesperiidae families during both dry and rainy seasons. Further, more species were sampled in the dry season (47 species) compared to the rainy season (28 species). Of these, 19 species occurred in both dry and rainy seasons. Twenty-eight were only found during the dry season and 9 were only found during the rainy season. We recommend continuous studies in Rugezi and other marshlands to enrich the findings of this study.