Morphology of long- and short-day eggs of Aedes atropalpus and A. epactius (Diptera: Culicidae).

Scanning electron micrographs are used to document differences in the shape and fine structure of long-day (16:8 [L:D] h) and short-day (8:16 [L:D] h) eggs of Aedes atropalpus (Coquillett) and Aedes epactius Dyar & Knab from Illinois. Both shape and structural detail differed much more in A. atropalpus than in A. epactius. Long-day eggs of A. atropalpus were significantly longer and narrower; their outer chorionic cells on both the ventral (upper) and lateral surfaces were significantly smaller in area, with fewer small tubercles, and the detailed structure, shown in a comprehensive series of micrographs, was distinctly different than those of the short-day eggs. Dimensional differences of the whole egg were much less apparent in A. epactius; only width was significantly greater in short-day eggs. However, the ventral and lateral chorionic cells in the 2-d length groups showed the same highly significant differences in area and numbers of small tubercles as in A. atropalpus. Fine structural differences also were much less apparent in the eggs of A. epactius.