Researching how the malarial mosquito A. gambiae developed resistance to common pyrethroid insecticides, the authors discovered how natural selection had enabled this insect population to develop resistance. They analyzed the gene-expression profiles of insecticide resistant A. gambiae populations from Burkina Faso and Côte d'Ivoire, finding higher than normal expression of genes that encode a family of chemosensory proteins, called sensory appendage proteins (SAPs). This protein specifically binds to pyrethroids that penetrate the moquito's hard exterior when it lands on a bed net (mosquito net), and thus prevents the insecticide from exerting its toxic effect by sequestering it and preventing its action on the mosquito's nervous system by promoting the breakdown of the pyrethrin. The authors also found that the expression of this protein is enhanced in the legs of the mosquito and mostly at the tips where the legs come in contact with the bed net. (Order of authorship in the original paper: Ingham, Anthousi, Douris, et al.)

(Thanks to Juan Weiss for this reference and its interpretation.)