Leg Autotomy: A Novel Mechanism of Protection Against Insecticide Poisoning in Diamondback Moth (Lepidoptera: Plutellidae)

Abstract

Adult diamondback moths, Plutella xylostella (L.), often autotomize one or both metathoracic legs after tarsal contact with insecticide residues. Moths that dropped legs after walking on fenvalerate residues had lower mortality and higher recovery from knockdown than those that did not autotomize. In experiments with 14C-labeled fenvalerate (250 ng/cm2), the concentration of fenvalerate and metabolites was significantly lower in moths that dropped legs (310 ± 26 ppb [x ± SEM]) than those that did not (392 ± 23 ppb). The concentration of fenvalerate and metabolites in autotomized legs was more than 10 times greater than the concentration in moth bodies. Two laboratory colonies of diamondback moth reared under identical conditions differed in their rate of leg drop, suggesting intraspecific genetic variation for autotomy. Result suggest that leg autotomy gallows diamondback moths to avoid the full effects of insecticide poisoning by eliminating part of the dosage.