Fourth-instar larvae of Aedes aegypti synthesize two types of hexamerins, Hexamerin-1 (AaHex-1) and Hexamerin-2 (AaHex-2), whose subunits are distinguished by different methionine and aromatic amino acid contents. In early female pupae only the methionine-rich AaHex-1gamma subunit accumulates to two-fold higher levels than in males. To investigate the relationship between hexamerin structure and the roles of Hex-1 and Hex-2 during mosquito development and reproduction, we have cloned and sequenced cDNAs encoding the AaHex-2alpha, -2beta and AaHex-1gamma subunits. Comparison with other insect hexamerins revealed that the Aedes Hex-1 and Hex-2 proteins belong, respectively, to the two hexamerin subfamilies previously defined for brachyceran Diptera. Probes specific for the Hex-2alpha and Hex-1gamma transcripts showed that expression of both genes follows the same developmental timetable. However, greater Hex-1gamma mRNA accumulation may contribute to the higher levels of Hex-1 gamma protein in early female pupae.