Tin effects of sub-lethal doses of malathion on the weight, fecundity and longevity of Ischiodon scutellaris Fabr. Were studied. The 1.1) 50 values for malathion, applied topically to the third instar larvae, were 2b. 9 x 10'2 (24h) and 18.7 x 1 0 ' 2 (48h) pg/larva; the LD 95 values were 146 x 10'2 (24h) and 127.6 x 102 (48h) pg/larva. There was a significant d ifferen ce (at 5% level) in the weight and longevity o f fem a le Pies treated, at the third larval instar stage, with differ en t doses o f malathion. A similar weight difference (at 5% level) was n o ted be tw e en pupae treated at the larval stage. Measurable latent to x ic ity was evident for malathion. The LD 50 f r direct to x icity was 4 1 .7 x 10~2 pg/larva and fo r total to x ic ity it was 21.4 x 10' 2 µg/larva