: In recent times, focus on plant research has increased all over the world and a large body of evidence is being collected to evaluate immense potential of medicinal plants used in various traditional systems. In this regard, the present study was conducted to evaluate the bioactivity of a commonly used medicinal plant Cassia fistula against newly selected Bombyx mori (silkworm) larvae. C. fistula pods were extracted using water, methanol, ethanol, hydro-methanol (1:1) and hydro-ethanol (1:1) and were assayed for their activity against Bombyx mori. Methanol extract of C. fistula at concentration of 100 mg/L killed half (LC50) of Bomyx mori larvae under study. Bomyx mori LC50 for other C. fistula extracts were 400 mg/L for ethanol and hydro-methanol, 800 mg/L for hydro-ethanol and 1600 mg/L for aqueous extract. From the results of the present study it can be concluded that Bombyx mori lethality bioassay can be considered a useful preliminary tool for plant extract toxicity evaluation. The main objectives of the present study was to develop a new and simple assay to evaluate claims from traditional, tribal and advanced medicinal lore to suggest directions for future clinical research and commercial importance that could be carried out by local investigators in developing regions.

muhammad asif hanif ,