The most abundant proteins in haemolymph of honey bee (Apis mellifera) larvae and pupae are hexamerins. These haemocyanin derived proteins are produced by a larval organ „fat body“ and serve as a source of aminoacids for the development of pupae that do not consume food. Furthermore, there has been an evidence that hexamerins act as juvenile-hormone binding proteins but the mechanism remained unknown. Here we present a structure of native hexamerin 70b, isolated from bee pupae, determined to the resolution of 2.0 Å by X-ray crystallography. Hexamerin 70b forms hexamers with 32 symmetry. Each subunit contains an enclosed hydrophobic cavity occupied by one molecule of putative juvenile hormone. We suggest that the juvenile hormone can be released only upon proteolytic digestion of hexamerin. Therefore, the hexamerin consumption is linked to release of free juvenile hormone that may affect development of pupae. This regulation mechanism might be universally conserved among holometabolous insects.