The most abundant proteins in haemolymph of larva and pupa of holometabolous insects are hexamerins. Hexamerins function as a source of amino acids for development during non-feeding stages of life cycle. Furthermore, there has been an evidence that hexamerins act as juvenile hormone binding proteins. However, the details of this interaction remain unknown. Here we present the crystal structure of native hexamerin 70b, isolated from honeybee (Apis mellifera) pupae, determined to 2.0 Å resolution. Hexamerin is a homohexameric complex with D3 symmetry and each subunit possesses an enclosed hydrophobic cavity occupied by a molecule of juvenile hormone. Upon proteolysis of hexamerin the hormone is released into haemolymph and affects the development of pupa. We propose that this novel mechanism of hexamerin-based regulation might be conserved among holometabolous insects.