KK Sharma*, R Ramani, D Saha & B Baboo
Indian Institute of natural Resins and Gums, Namkum, Ranchi – 834 010 (Jharkhand)
Received 11th February, 2009; revised 22nd July, 2009
Abstract : Lac insects are exploited for their products of commerce viz., resin, dye and wax. India is privileged in being the world leader in production as well as export of lac. About 50% of the total world demand is fulfilled by the country. At present, production of raw lac in the country is approximately 22,000 metric tons per year. The major lac producing states are Jharkhand (36% of the country’s lac production), Chhattisgarh (37%), West Bengal (12%) and minor lac growing states like Orissa, Gujarat, Maharashtra and Assam. Lac cultivation has traditionally been carried out by tribals inhabiting forests. Over three million tribals inhabiting these states are engaged in lac cultivation for subsidiary income. About 28% of their agricultural income comes from lac. Lac insects and their host plants play an important role in economics of lac growers. Lac-culture is turning out to be an important component of Joint Forest Management for peoples’ participation in resource generation, management and sharing of benefits. It has potential to arrest deforestation and permit gainful utilization of vast natural wealth. Lac culture offers entrepreneurial opportunities and is uniquely suited to the economy and social structure of our country.
Of the nine genera and 89 species of lac insects found in the world, India has 19 species under two genera i.e. Paratachardina and Kerria. Resin produced by Paratachardina spp. is of little commercial value but these are very potential bio control agents for managing weeds. Lac insects belonging to Kerria are purposely cultivated for their products of commerce viz., resin, dye and wax. Yield of lac is dependent on various biological attributes of the insect. Hence, for evolving an insect with desirable characteristics, it is of considerable importance to know, how and to what extent the different attributes are interdependent. Eight stocks of lac insects belonging to three species i.e. Kerria lacca, K chinensis and K. sharda were studied. Significant variations were found in productivity linked parameters viz., life period, settlement density, fecundity, size and resin produced. Time taken to complete one generation varied from 98 to 268 days. Different lac insects showed varied density of settlement (80 – 264 per sq. cm.). The density under excess brood condition increased significantly and exhibited ‘crowding’ effect. Average resin output per female varied between 6.48 mg to 20.94 mg and fecundity varied between 276 and 748. Qualitative differences in body colour showing crimson, yellow, albino (white) and ‘cream’ have also been observed. A strong and positive correlation was found among size, fecundity and resin output which suggest that if genetic segregation is contributing appreciably to the variance of these traits, the genetic correlation among these will be in the desired direction. Hence, genetic improvement in any of these traits would be expected to produce favourable changes in the others as well which can be exploited for evolving insects with desired characteristics.