The ultrastructure of adhesive device or the pulvilli, pad-like structure between the tarsal claws of the legs, is presented in the blowfly (Calliphoridae), housefly and relatives (Muscidae), and flesh fly (Sarcophagidae) through scanning electron microscopy. The blowfly species were Chrysomya chani, Chrysomya nigripes, Chrysomya pinguis, and Chrysomya villeneuvi; while those of the housefly and relatives were Musca domestica and Hydrotaea chalcogaster, respectively. Fresh fly species included Boettcherisca peregrina and Liosarcophaga dux. Numerous tenent setae were observed on the ventral side of the pulvilli. Two features of the tip of the tenent setae were found as a spatula-like (in C. chani, C. pinguis, C. nigripes, M. domestica, H. chalcogaster, B. peregrina, and L. dux) and spoon-like tip (in C. villeneuvi). Transmission electron microscopy of the tenent setae in M. domestica revealed the electron-lucent centrally located, suggesting an adhesive substance. These results provided anatomical information that allow us to not only understand the successful attachment of flies to smooth surfaces but also clarify their role as a mechanical carrier of microorganisms.
The surface ultrastructure of all larval instars of Chrysomya rufifacies (Macquart) is described by means of scanning electron microscopy (SEM). Morphological changes were greatest from the first to the second instar, but less from the second to the third instar. Most of these changes involved the structure of the anterior spiracle, posterior spiracle, integument of the body, and mouthhooks. Modification of the mouthhooks, especially in the third instar, are helpful in explaining the ferocious feeding ability of the older maggots. The common name of "hairy-maggot" for C. rufifacies is only appropriate for the second and third instars because of their elongated tubercles along the body, whereas this name is not descriptive of the first instar that lack tubercles.
Morphology of the alimentary canal of the mature third instar larva of the blow fly, Chrysomya megacephala (F.), was examined using light, scanning, and transmission electron microscopy. Salivary structures consist of a single median deferent duct that bifurcates into efferent ducts connected to paired, tubular salivary glands comprised of closely packed conical-shaped epithelial cells with large nuclei. The crop occurs as a large, swollen diverticulum of the digestive tube and is lined internally with convoluted cuticle (epicuticle and endocuticle). The esophagus is a simple, straight tube internally lined with cuticle and externally encompassed by muscle fibers. The cardia is a bulb-like structure composed of anterior foregut tissue and posterior midgut tissue from which the peritrophic membrane (PM) is produced. The midgut begins within the cardia which is flanked posteriorly by four tubular gastric caeca that are lined internally with four to five layers of cuboidal epithelial cells bearing microvilli. Midgut tissue is lined with simple cuboidal epithelium whose cells are filled with numerous secretory granules and possessed long microvilli facing the lumen. A peritrophic membrane is contained within the midgut lumen. The larval hindgut consists of the pylorus, Malpighian tubules, ileum, colon, rectum, and anus, posteriorly. The pylorus is characterized by a single layer of epithelial cells encircled by a muscular layer and the presence of PM within the lumen. Malpighian tubules each diverge into two tubular structures totalling four long tubules of long chained cuboidal cells bearing microvilli internally. The wall of the ileum is comprised primarily of a monolayer of cuboidal epithelial cells with large oval nuclei and more intense muscular fibers surrounding the periphery. A cuticular layer surrounds the lumen containing the PM. This inner cuticle consists of a thin epicuticle that is electron-dense; whereas, the endocuticle is much thicker but less electron-dense. Myo-epithelial cells are dense in the anal region, where the PM persists.
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