Larval ecology and development of swallowtail butterfly, Papilio nireus (Lepidoptera: Papilionidae) on wild citrus species (Rutaceae) in Kenya

Butterflies are among the most important biodiversity components within the ecosystem. They are pollinators of both wild plants and agricultural crops. Swallowtail butterfly, Papilio nireus is a common species with a wide range of distribution in Sub-Saharan Africa. In Kenya, it’s commonly found in Taita hills on diverse species of forest trees and shrubs amongst them, wild citrus (Rutaceae), Clausena anisata and Toddalia asiatica. Little information on the larval ecology and development on its host plants makes species management and conservation difficult. This study, therefore, analyzed larval ecology and development of P. nireus on two host plants, C. anisata and T. asiatica in captivity in Ngangao forest, Taita Hills for two seasons from February to July 2021. Egg incubation period was significantly longer on T. asiatica than on C. anisata . Similarly, the total larval period was significantly higher on T. asiatica than on C. anisata . The development period from egg to adult was shorter on C. anisata (60.26 days in the 1st season, 63.15 days in the 2nd season) than on T. asiatica (66.44 days during the 1st season, 69.01 days in the 2nd season). However, the sex ratio and larval weight of P. nireus varied with season and the rearing host plant. The 1st season population had a sex ratio that was female-biased on both C. anisata and T. asiatica while in the 2nd season, sex ratio on C. anisata was male-biased and that of T. asiatica female-biased. In the 1st season, fourth larval instar weight was higher on T. asiatica (142.50 mg) than on C. anisata (88.70 mg) while in the 2nd season, the weight was higher on T. asiatica than on C. anisata from the second instar to the fifth instar. Findings from this study showed that the larval period and development of P. nireus was shorter on C. anisata than on T. asiatica. Therefore, the study revealed that both C. anisata and T. asiatica were host plants for this butterfly species but C. anisata was the most suitable host plant in the area of study. The study recommends conservation of both host plants for the species survival within its habitat.