Some Aspects on the Biology of the Groundnut Borer Caryedon Serratus (Olivier) (Coleoptera: Bruchidae)
Abstract:
Groundnut borer, Caryedon serratus (Olivier) (Coleoptera: Bruchidae) is the only insect species known to infest kernels and intact pods of groundnut, thus it potentially becomes the most important major store pest of groundnut. The literature on the biology of C. serratus is scanty and is only available for the other bruchid, Callosobruchus macullatus (F) and the other related species, C. chinensis (L). For this reason, this work aimed at studying the biology of this species. The studies included mating process and frequency, developmental period of the eggs, larvae, pupae and adults of sexes, fecundity of females, preference of the females to oviposit on shelled and unshelled groundnut and the sex ratio of the progeny. The results revealed that: Mating occurred soon after adult emergence, took about 16-18 minutes. Both females and males mated once during their lifespan. The mean incubation period of the eggs was 6.28 and 5.33 days, larval development was completed in 16.71 and 15 days, pupal stage lasts for about 13 and 13.3 days, the mean adult longevity was 13.42 and 12 days and the total life cycle was completed in 50 and 45 days for females and males, respectively. The larvae undergo three moults and the mean larval instars duration were 3, 3.7, 3.8 and 4 days for the first, second, third and fourth instar respectively, while prepupal period took 2 days. Females deposited significantly more eggs on unshelled than on shelled groundnuts (38 and 28/female). The pre-oviposition period was one day, oviposition period ranged between 2-4 days and the post-oviposition period ranged between 3-5 days. The oviposition started on the second day and reached the peak on the third day. The eggs hatched and gave males and females, at 1.17:1 ratio.
