Abstract: The pure compound annotemoyin-1 isolated from the chloroform extract of the seeds of Annona squamosa Linn. was evaluated for its pesticidal activity against both adults and different instars of Tribolium castaneum (Herbst) under laboratory condition. The LD50 values of the pure compound were determined both for adults and different instars of larvae. The LD50 values of the compound were 579.67, 394.89, 243.10, 612.92, 366.95, 315.18, 636.12, 423.30, 333.67, 684.88, 449.28, 101.68, 742.69, 525.93, 199.41, 792.38, 609.08, 191.70, 827.43, 615.36, 221.13, 920.54, 693.10 and 429.42. These results demonstrated that the earlier instars were more sensitive to the compound than those of late instars as well as adults.