THE FERTILIZATION CANAL IN PLODIA INTERPUNCTELLA (HÜBNER) (PYRALIDAE: LEPIDOPTERA)

The spermathecal duct of Plodia interpunctella (Hübner) was studied with light and transmission electron microscopy. The lumen in the duct is enclosed by a thin chitinous wall that has a thicker band that spirals along the length of the duct. The thick spiral band pinches off part of the lumen and creates a smaller canal, which it encloses. Although the two canals are not separated, the duct appears to have a double lumen. The thin wall of the main canal provides a flexibility in which the lumen widens or narrows concomitantly with contractions of the spermatheca and the portion of the duct adjoining the spermatheca. Sperm is transferred from the spermatheca to the vestibulum where the egg is fertilized. The distention of the canal and contractions of the spermatheca thus account for the speed at which eggs are fertilized and deposited.