Leg Autotomy of Adult Diamondback Moth (Lepidoptera: Plutellidae) in Response to Tarsal Contact with Insecticide Residues

Abstract

Up to 74% of adult diamondback moths, Plutella xylostella (L.), autotomized one or both metathoracic legs after tarsal contact with insecticide residues. In bioassays with fenvalerate, the LC50, was 478 ng/cm2, and the autotomy response peaked at 100 ng/cm2. Scanning electron microscopy showed a smooth abscission at the joint between the trochanter and femur. In comparison with moths retaining all their legs, those that autotomized recovered faster from knockdown. Leg autotomy in insects was thought to be primarily a mechanism for escaping entrapment, but it may aid in escaping the effects of toxins.