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Effective control of diseases transmitted by <i>Aedes aegypti</i> is primarily achieved through vector control by chemical insecticides. However, the emergence of insecticide resistance in <i>A. aegypti</i> undermines current control efforts. Arachnid venoms are rich in toxins with activity against dipteran insects and we therefore employed a panel of 41 spider and 9 scorpion venoms to screen for mosquitocidal toxins. Using an assay-guided fractionation approach, we isolated two peptides from the venom of the tarantula <i>Lasiodora klugi</i> with activity against adult <i>A. aegypti.</i> The isolated peptides were named U-TRTX-Lk1a and U-TRTX-Lk2a and comprised 41 and 49 residues with monoisotopic masses of 4687.02 Da and 5718.88 Da, respectively. U-TRTX-Lk1a exhibited an LD₅₀ of 38.3 pmol/g when injected into <i>A. aegypti</i> and its modeled structure conformed to the inhibitor cystine knot motif. U-TRTX-Lk2a has an LD₅₀ of 45.4 pmol/g against adult <i>A. aegypti</i> and its predicted structure conforms to the disulfide-directed β-hairpin motif. These spider-venom peptides represent potential leads for the development of novel control agents for <i>A. aegypti</i>.