From ZooTerms (Dictionary of Invertebrate Zoology)
Arthropoda) The main body cavity, the embryonic development of which differs from that of a true coelom, but which includes a vestige of that true coelom that emanates from the blood spaces of the embryo, or remnants of the blastocoel after invasion of the latter by the mesoderm.hemocoel also haemocoele (noun; Greek haima, blood; koilos, hollow): 1. (
2. (Mollusca) The main body cavity.