Observations on the morphological ultrastructure of eggs of Ochlerotatus (Protomacleaya) terrens (Diptera: Culicidae) were conducted by using scanning electron microscopy. Morphometry of the principal structures was obtained with the aid of Semafore analysis software. Eggs of Oc. terrens from females caught in the Biological Reserve of Tinguá, State of Rio de Janeiro, Brazil, were utilized. The eggs presented elliptical outlines, with a length of approximately 649.0 microm and width of 168.7 microm. The egg index (length to width ratio) was 3.85 microm. The exochorion had hexagonal and sometimes pentagonal ornamentation. Inside the chorionic cells were small, well-distributed tubercles with a large range of sizes. The micropylar apparatus, located in the anterior region of the egg, presented a collar with a poorly visible frame, with borders of indeterminate extent and margins without a defined transition area, and a thickness of approximately 1.8 microm. The micropyle was plugged.