The effect of topical application with 10, 20 and 30 $mu extrm{g}$/ml cortisone and hydrocortisone to the fifth stadium larvae of the silkworm, B. mori on fat body glycogen, protein, total lipids, phospholipids, neutral lipids and haemolymph trehalose and protein has been studied. The fat body glycogen haemolymph trehalose significantly decreased in all the treated groups except in the 10 and 20 $mu extrm{g}$/ml treated groups. The fat body protein increased significantly in all the cortisone and hydrocortisone treated groups except in the group treated with 10 $mu extrm{g}$ hydrocortisone. Whereas that of haemolymph protein significantly increased in all the groups treated with cortisone and hydrocortisone. The total lipids, phospho1ipids and neutral lipids of the fat body decreased significantly in all the groups treated with cortisone and hydrocortisone when compared with that of carrier control.