Tissues of  Bombyx mori mature larval instar can be classified into two major groups according to the presence or absence of lectin mRNA; i. e. hybridization  of the mRNA with the 50 KDa lectin probe: The first group contains fat bodies, midgut, fore and hind wings discs, malpighian tubes, prothoracic gland, anterior silk gland and ovary.These tissues had active lectin gene which was transcribed into lectin mRNA. Therefore, expression of lectin gene was detected in these tissues. The second group of tissues includes testis, trachea, suboesophageal ganglion and thoracic ganglia. They did not give any indication for the presence of lectin gene. Thus, these tissues may have a silent lectin gene or lack lectin mRNA which is responsible for encoding lectin.