Ultrastructure of the labellar glands in the female black blowfly, Phormia regina (Meigen) (Diptera: Calliphoridae)

Abstract

The fine structure of the labellar glands in adult, non-diapausing, female Phormia regina is described. These epidermal glands, located on both sides of the proboscis in the distal portion. of the-haustellum, are comprised of unicellular secretory cells coupled to an efferent ductule which is accompanied by an ensheathing ductule cell. The cuticular ductule within the secretory cell empties an extracellular, microvillus cavity, the end apparatus. The ductules condense to form a pair of ducts which traverse the epidermal layer of cells around the hypoglossal sclerite. Septate junctions are found between secretory cells and ductule cells but not between any other cell borders. Tracheae are seen occasionally between secretory cells or between secretory and epidermal cells. The function of the labellar glands remains unknown; however, their possible function is discussed with reference to previous reports.