External morphology of some eggs of stored-product moths (Lepidoptera pyralidae, gelechiidae, tineidae)

Abstract The eggs of closely related stored-product moths are difficult or impossible to separate by light microscopy. Although the scanning electron microsocpe (SEM) reveals details of the chorion that are useful in determining species, no comparative SEM studies of these eggs have been published. A study was therefore undertaken to determine the features of chorionic sculpturing that are useful in identifying the eggs of stored-product moths and to construct a taxonomic key to some of the more important species. Surface features of the chorion considered in conjunction with overall shape were adequate to separate all the species examined. The most useful diagnostic characters included the pattern of ridges, carinae, and cells; the structure of the aeropyles; and the texture of the chorion on the cell discs. Following are diagnostic characters for the 10 species studied: The egg of Sitotroga cerealella is fusiform, truncate at the anterior end, and marked by a reticulate pattern of prominent longitudinal ridges joined by lesser cross ridges. That of Tineola biselliella is subcylindrical and marked by a pattern of irregular polygons; the primary cells are oval to nearly circular, and the aeropylar openings are unguarded. The eggs of Galleria mellonella and Achroia grisella are also marked by irregular polygons. These eggs, however, are spheroid, ellipsoid, ovoid, or obovoid; the primary cells are wedge-shaped with rounded outer margins; and the aeropylar openings are surrounded by distinct collars. In G. mellonella, the pattern of polygons is at least faintly visible over the entire surface and the carinae surrounding the primary cells are of uniform width, but in A. grisella the pattern is limited to the anterior end and the carinae are conspicuously broader around the outer margins of the primary cells. The eggs of the remaining species are marked by reticulate patterns of intersecting sinuous ridges. The cell discs of Plodia interpunctella and Anagasta kuhniella are roughened by numerous small excrescences, and most of the ridges bear carinae along their crests. In P. interpunctella, the excresences are rounded, the carinae are prominent and more or less continuous over the entire surface, and the primary cells are subequal. In A. kuhniella, the excresences are sharp edged, the carinae are weak and often disconnected, and some of the primary cells are much larger than others and overlap the ends of adjacent cells. The cell discs of Cadra figuldella, Ephestia cautella, Ephestia elutella, and Corcyra cephalonica are smooth. In C. figuldella, E. cautella, and E. elutella, the ridges lack carinae except in the micropylar area and there are prominent tubercles at most ridge intersections. Cadra figuldella has widely spaced ridges and broad cell discs, while the Ephestia species have closely spaced ridges and restricted cell discs. The aeropylar openings of E. elutella are surrounded by distinct collars, but those of E. cautella are unguarded. The eggs of C. cephalonica lack prominent tubercles; carinae extend well beyond the micropylar area on the anterior end, and there are a few short carinal segments on the posterior end.