KEN FENING1, ESTHER KIOKO2, SURESH RAINA2, JONES MUEKE3
1Council for Scientific and Industrial Research - Crops Research Institute, Plant Protection Division, Ghana
2International Centre of Insect Physiology and Ecology, Commercial Insects Programme, Kenya
3Kenyatta University, Zoological Sciences, Kenya
The African wild silkmoth, Gonometa postica Walker (Lepidoptera: Lasiocampidae) is known to produce high quality silk comparable to that of the domesticated silkmoth, Bombyx mori L. (Lepidoptera: Bombycidae). Currently, it is the species being utilised for wild silk production in Kenya and is known to feed on several Acacia species. The effect of food plants [Acacia elatior Brenan, A. tortilis (Forssk.) and A. nilotica (L.) Del] on the developmental time of G. postica larvae and the quality of their cocoons were studied in the Imba and Mumoni forests of Mwingi, eastern Kenya, during the long (March-May) and short (October-December) rainy seasons of 2006 and 2007. Larvae were reared in semi-captivity in net sleeves attached to branches of the plants. The period between hatching of eggs and spinning of cocoons as well as weight as determinants of cocoon quality were recorded. In addition, collections of cocoons from the wild were done in the two forests from the same host plants for assessment of their quality. In the cage experiment, larval developmental period and quality of cocoons differed according to food plants, seasons, and sites while quality of cocoons sampled from the wild habitat was similar for all food plants and seasons but varied according to site. Generally, there was a positive correlation between weight of cocoon, its length and width for the two seasons for both the semi-captive population and those from the wild. Larvae reared on A. elatior had a shorter developmental period and higher cocoon quality than those raised on A. tortilis and A. nilotica. Generally, temperature and relative humidity significantly influenced larval developmental time and the effect was both positive and negative. Rainfall was generally higher in Mumoni than in Imba. The above findings will help improve the semi-captive rearing of G. postica to increase the quantity and quality of cocoons for silk production.
Keywords: Acacia species, cocoon quality, gonometa postica, larval developmental period, semi-captive rearing