Abstract
Coagulation and phagocytosis are defense reactions which insects use in response to introduction of foreign particles into their hemocoel. Coagulation occurs within 10 s of injection of latex beads and ink particles into a midfifth larval instar of C. ethlius. A stringy, flocculent coagulum forms, trapping the particles and hemocytes. The hemocytes then phagocytize the particles. The coagulum stains with alcian blue and lanthanum and dialyzed Fe. The surface coat of granular hemocytes stains differently after coagulation has taken place with the same stains and with ruthenium red. There is no corresponding change in staining of the surface of plasmatocytes.