Effects of Synthetic “Queen Substance” and Analogues on Survival, Molting, and Metamorphosis of Aedes aegypti12

Abstract

Effects of synthetic “queen substance” (9-oxotrans-2-decenoic acid) and several related chemicals on survival, molting, and metamorphosis of the yellow-fever mosquito, Aedes aegypti (L.), were investigated. The effects of queen substance applied to the 4th-stage larvae included: (1) “rapid” mortality in the treated stage caused by “acute toxicity,” (2) delay in molting of larvae, and (3) inhibition of metamorphosis which involved (a) failure of ecdysis caused by nondetachment of the old cuticle during the larval-pupal or pupal-adult molt or (b) failure of pupal or imaginal differentiation resulting in death of the insect. Of the 5 developmental stages of the 4th-stage larvae, the first was most susceptible to rapid mortality and molting delay, while the fourth stage was susceptible to metamorphosis inhibition. Trans-2-decenoic acid had much greater acute toxicity than queen substance but hardly inhibited metamorphosis. The saturated and unsaturated acids with chain length 10-13 carbon atoms were more toxic than those with a shorter chain length. An increase in chain length above 13 C atoms markedly decreased the acute toxicity of the saturated acids but tended to increase toxicity of unsaturated acids. Of these, linoleic and linolenic acids were the most toxic. The presence of an oxo-group in a saturated or unsaturated 8-10 carbon fatty acid remote from the carboxyl group reduced acute toxicity and increased inhibition of metamorphosis. Methyl esters of such acids, however, had both greater acute toxicity and also higher potency for metamorphosis inhibition than queen substance.