The formation of the cuticular ridges in the larval pharynx of the blowfly (Calliphora vicina R.-D.)

A method for rearing blowfly larvae giving good synchronization of growth is described. Electron microscope studies showed that the lateral lamellae of the pharyngeal ridges each have a swelling at the tip, and that the lamellae from adjacent ridges are interdigitated in a regularly alternate pattern. Formation of the ridges in the second-instar larva begins 8 h before the moult when the four rows of partially syncytial epidermal cells lying beneath the floor of the pharynx begin to form nine dorsal projections. These lengthen and gradually take up the form of the ridges, the fine divisions which are the lateral lamellae being the last feature to develop. After a two-layered epicuticle has been formed the cytoplasm rapidly withdraws from the ridges leaving them, and the new floor of the pharynx, strengthened by a network of fibres. At the moult a further zonse of cuticle, showing parallel striations, is added to the base of the ridges. The lateral lamellae are epicuticular structures. The importance of the intracellular formation of cuticle is discussed.

I should like to thank Dr P. Tate under whose supervision this work was carried out for helpful advice, and wish to acknowledge financial support from the Agricultural Research Council in the form of a Postgraduate Studentship.