The effect of topical application with 200,400 and 600 $mu$g/ml 2,4-Dichlorophenoxyacetic Acid (2,4-D) and Naphthoxyacetic Acid (NOA) 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 significantly increased in all the groups treated with 2,4-D whereas there is no significantly change in fat body glycogen in all the groups treated with NDA. However, the haemolymph trehalose was significantly increased in all 274-D and NOA treated groups except in the groups treated with 400 and 600 $mu$g/ml 2,4-D where the increase was not significant.The fat body protein did not show any significant change in all groups treated with 2,4-D and NOA except in the groups treated with 200 $mu$g/ml 2,4-D where the fat body protein was significantly increased. The total lipids, phospholipids and neutral lipids of the fat body increased significantly in all the groups treated with 2,4-D and NOA when compared with those of the corresponding parameters of the carrier control.