Hemolymph coagulation began almost immediately after wounding in mosquito, Armigeres subalbatus, (Coquillett) larvae. Immunocytochemical localization showed that prophenoloxidase (pro-PO) was distributed in the wound site. In the initial wounding, coagulation and wound plug formation occurred with granulocyte migration. The hemocytes lysed and released granular materials around the wound site, prophenoloxidase being mostly localized in granules and cuticle. In the second phase of wound healing, melanin accumulation occurred at the wound site along the margin of the cuticle and rapidly increased in thickness. Immunogold-labeled pro-PO was localized in vacuoles, melanins, and cuticle, with the gold particles labeled intensely on the undarkened cuticle and weakly on the darkened cuticle. It is believed that pro-PO is activated upon wound initiation to produce melanin product and deposited on the cuticle. In the final phase of healing, scab melanization and pro-PO immunogold localization were reduced and accompanied by epithelial cell regeneration. This proenzyme was localized in vesicles and flocculent materials, but was absent in the melanized scab. Our results further indicate that pro-PO was present in granules, cuticles, epithelial cells, vacuoles, and flocculent materials but not in melanized scab and coagulated clot. The pro-PO immunogold particles labeled intensely in the initial wounding but weakly in the final phase. Our observations also suggest that pro-PO is released from granulocytes by cell rupture, synthesized or stored in granulocytes, and then is released into the wound site via the cytoplasmic granules. This study indicates that the pro-PO is involved in numerous physiological roles in the process of wound healing in this mosquito.

The wound-healing processes in the mosquito Armigeres subalbatus (Coquillett) were observed with electron microscopy. The initial reaction involved wound contractions and aggregation of injured surface tissues, cell debris and movement of granulocytes toward the wound. Granulocytes first aggregated around the surface of the wound and many filamentous filopodia protruded to connect with cytoplasmic strands. These strands were then interconnected to form a network coagulum resulting in wound closure to prevent body fluid loss. Granulocytes lysed on the wound-site and released granular materials around the wound, inducing localized clot formation. These results suggested that wound-healing in this mosquito species involved both humoral and cellular reactions. The latter reaction involved the movement of plasmatocytes to the basement membrane of the epidermis beneath the wound-site and epithelial cells regeneration. Our observations revealed that wound-healing in A. subalbatus involves the wound contraction, formation of a temporary cellular clump, scar formation, basement membrane formation, and reepithelialization. The larvae neither discarded the wound scar nor secreted a new cuticle until the next molting. Based on the ultrastructural observations, it is suggested that the wound-healing reaction in A. subalbatus was probably a typical response employed by other members of the family Culicidae.