A new insecticidal compound PF1018 was isolated from the culture broth of Humicola sp. It exhibited insecticidal activity against a wide range of critical pest species. The structure of PF1018 was determined to be (7aS)-2-((2E)-1-hydroxy-3-((1S,3aR,4R,5R,7aR)-3a,4,5,7 a-tetrahydro-1,3,5,7- tetramethyl-5,1-((3S)-(Z)-2,3-dimethylpropeno)-1H-inden-4-yl )-2- propenylidene)pyrrolizidine-1,3-dione, by NMR spectral analyses coupled with X-ray crystallographic analysis and chemical degradation study.