The patterns of the endochorionic sculpturing and the thickness of the endochorion of eggs from the females of the Psorophora confinnis complex collected from 10 geographic locations in the United States were studied with scanning electron microscopy. Eggs deposited by members of the Ps. confinnis complex in California have 3 distinct patterns not found in eggs of this complex collected from Arkansas, Florida, Louisiana, Mississippi, New Jersey and Texas; thus indicating that Ps. columbiae in California may be genetically different from Ps. columbiae found elsewhere in the United States. No seasonal or geographic variations in the inner chorionic patterns or endochorionic thickness were detected for eggs from eastern populations of the Ps. confinnis complex.