Sarhad J. Agric. Vol.24, No.1, 2008 EFFECT OF LIGHT AND DARK EXPOSURE ON THE DIFFERENT LIFE PARAMETERS OF SILK WORM, BOMBYX MORI L. (BOMBYCIDAE: LEPIDOPTERA) Toheed Iqbal*, Mian Inayatullah*, Amna Sadozai** and Imtiaz Ali Khan* ABSTRACT The performance of the Japanese race of silkworm, Bombyx mori L. (Bombycidae: Lepidoptera) was studied at Sericulture Wing, Forest Department Peshawar under laboratory conditions of 25 + 2 ºC temperature and 70 + 10 % relative humidity in complete dark (24 hours) and a complete light (24 hours) condition. The results showed that mean life cycle of B. mori was 62 days in dark and 68 days in light. The diurnal variation in the activity persisted in constant darkness, but was suppressed by constant light. Mean cocoon weight was 1.06 gm in dark and 0.9 gm in light. Mean shell weight in dark and light was 0.2 gm and 0.16 gm, respectively. Shell ratio in dark was 19.40 gm, whereas it was 18.35 gm in light. Percentage of sex ratio (F:M) was 56:44 in dark, whereas it was 42:58 in light. Mortality percent of larvae kept in dark was lower (13.3 %) than in light (24.4 %). Mean fecundity of the adults emerged from larvae kept in dark and light was 112.6 and 46.7 eggs/f, respectively. Generally, that the duration of life cycle, cocoon weight, shell weight, percent shell ratio, percent sex ratio, percent mortality, and fecundity of the larvae reared in dark was significantly better than the larvae kept in light condition. Keywords: Bombyx mori, Light and Dark Exposure, Life parameters, Biology, Fecundity. INTRODUCTION Sericulture is the science of rearing silkworm for the commercial production of raw silk, and includes the operations, which are required for the production of silk fiber (Krishnaswami et al., 1973). The larvae of Bombyx mori L. (Bombycidae: Lepidoptera) are caterpillars that are about 4 cm long, including their horned tail. They are buff-colored with brown thoracic markings. The adults are moths with a 4 cm wingspan. They are also buff-colored, but have thin brown lines on their whole bodies (Herbison-Evans, 1997). Another silkworm, Bombyx mandarina appears to be a wild race of B. mori (Savela, 1998). Silk worm, Bombyx mori (should be B. mori) is the common species used for the production of silk. Silkworm undergoes complete metamorphosis that is their life cycle passes through four stages, egg (embryo), larva, pupa, and moth (adult) (Anonymous, 1998). Silk is mostly used in manufacturing of cloth. It is also used in making of surgical sutures, artificial blood vessel, tire lining, parachute, electric insulating material, oil protein and artificial vitamins. Waste material (excreta) of B. mori is used as an artificial diet for animals and as green manure for crops (Ishfaq and Ikram, 1999). In Pakistan, sericulture is practiced in all the four provinces and Azad and Jammu Kashmir. The main activity of natural silk production is practiced around the irrigated forest plantation of Changa Manga, Kamalia, Chichawatni and Multan in Punjab province (Anonymous, 1990). Pakistan’s economy largely depends on agriculture and its raw products. The production of raw silk is inadequate to meet requirements of the textile industry. If the textile industry is provided with adequate raw silk, Pakistan can not only save its precious foreign exchange (i.e., reduce imports), but can also improve its economy by exporting the surplus commodity. Since the majority of population lives in rural areas and villagers including men, women and children can increase their income through the rearing of B. mori in their spare time. The process of rearing is completed before wheat harvest. Even they can easily get two generations of B. mori one after the other (Ishfaq and Akram, 1999). Researchers have conducted experiments to find out high yielding strains of B. mori and mulberry. Different species of mulberry may have compositional differences and might lead to vary effects on B. mori growth and silk production (Mahmood et al., 1987). The growth rate of B. mori larvae and subsequent silk production depend mainly on the nutrient content of mulberry leaves. Fukuda (1960) reported that about 70% of silk protein produced by the B. mori is directly derived from the protein contents of mulberry leaves. The nutritive value of mulberry leaves varies due to species and leaf maturity of the plant. Hoffman and Subramanian (2005) found in their experiment on the role of light exposure on the final stages of development of Anopheles stephensi that there was a significant reduction in the development of adult mosquitoes when larvae were bred in the absence of light compared with the control group bred in alternating 12h light and 12h dark. It has been observed that electric light can affect the behavior of nocturnal insects. A high level of illumination causes night * Department of Entomology, NWFP Agricultural University Peshawar – Pakistan. ** Sericulture Wing, Forest Department, NWFP, Peshawar – Pakistan.