DRY SEASON STUDY OF NECROPHAGOUS INSECTS ASSOCIATED WITH CAVIA PORCELLUS (GUINEA PIG) CARCASS IN KADUNA, NIGERIA

Abstract

Necrophagous insects associated with decomposing carcass of Cavia porcellus were studied during the dry season in Kaduna, Nigeria. The carcass was placed inside a steel cage (81 x 53 x 45 cm) to prevent larger animals and birds from scavenging but allowing insects to have access. The cage was removed to expose the carcass and allow for recording of the progress of decomposition, collection of immature stages, taking of photographs and collection of adult insects. Sampling of adult insects was conducted with sweep nets above and around the carcass to assess species occurrence and abundance. Four decomposition stages were identified comprising fresh, bloat, decay and dry decay stages. The fresh stage lasted only one day beginning soon after the carcass was killed. The bloat stage was observed from day 2 till day 5 post killing. The decay stage commenced on day 6 when the carcass ruptured and lasted till day 9. The bulk of the biomass was removed during the decay stage as a result of the maggot feeding. Dry decay stage began about day 10 when the carcass started showing signs of dryness and continued until day 16 when the experiment was terminated. Three insect orders were encountered namely: Diptera, Coleoptera and Hymenoptera belonging to seven families and twenty one species. The order Coleoptera comprised three families and four species, with Hister beetle being the first to arrive during the bloat stage on day 2 and remained through the decay and dry decay stages of decomposition. No arthropod was recorded during the dry decay stage except one species each of Hister beetle and Messogalla ant. Species of Pheidole and Messorgalla ants (Hymenoptera) were the only species seen during the brief fresh stage but two other species of ants (Camponotus sp and Crematogaster sp) were recorded during the bloat stage. On the whole, diptera had the highest prevalence accounting for 75% of the total collection. The Calliphorids were represented by three species, the Sarcophagids by five species and Muscidae by three species. The abundance of the seven families of arthropods occurred in the order: Muscidae>Sarcophagidae>Calliphoridae>Formicidae>Histeridae> Curculionidae and Caracidae. The insects that emerged from the laboratory - reared immatures were all dipterans from the families Sarcophagidae (Sarcophaga exuberans and Sarcophaga villa) and Calliphoridae (Hemipyrellia fernandica, Phaenicia (L) sericata and L. infernalis).