Fine structure of the integumental glands of a termite soldier

The ultrastructure of some integumental glands occurring in the head, thorax and abdomen of K. flavicollis soldiers is described. The secretory units consist of two cells, the canal cell and the secretory cell (this latter filled with secretion granules). A cylindrical and distorted extracellular space, or reservoir, with an irregular outline is lined by short microvilli. The end-apparatus is made up of small overlapping cuticular laminae which in section resemble small wavy rods. The ample distribution of the units has led the authors to consider them dermal glands. Scanning electron micrographs confirm that the glands' activity consists in the secretion of material which then spreads over the surface of the integument. The dissimilar appearance of the secretion granules present in glands of different soldiers suggests that the electron-lucid granules and the granules with fibrils are two completely different secretions at different ages of the animal. The authors do not therefore rule out the hypothesis that these integumental glands may later produce or release pheromones.

Fine structure ofDrosophila wing imaginal discs during early stages of metamorphosis

Fine structural changes are described which occur in wing imaginal discs taken fromDrosophila prepupae at 120-128 hours of age. The first signs of cuticle formation appear at 124 hours in the tips of microvilli which extend into the peripodial cavity of the disc. A continuous epicuticular layer is evident at 126 hours, and the beginning of laminated endocuticle at 128 hours. Electron-lucid spaces appear in the apical regions of the cells at 122 and 124 hours. These are often clearly intercellular and contain membranous material, but sometime appear to be intracellular, or vacuoles. Their frequency decreases sharply after 122 hours, and begins to rise again at 126 hours. Junctional complexes between cells are present in all ages studied, consisting predominantly of long zonulae adhaerentes in the 120 h disc, of various attachment specializations, including septate desmosomes in the 128 h disc. Inclusions interpreted as lipid are found randomly scattered in the cytoplasm at 120 hours. They change in number, size, arrangement and location in later stages.Microtubules are widely distributed in discs of all ages reported; their function is thought to be cytostructural. A method of precise staging of prepupae based on ultrastructural criteria is proposed.

THE DISTRIBUTION AND IDENTIFICATION OF ESTERASES IN THE DEVELOPING EMBRYO AND YOUNG NYMPH OF THE LARGE MILKWEED BUG, ONCOPELTUS FASCIATUS (DALL.)

Aromatic esterase (A esterase, organophosphate-resistant esterase), aliesterase (B esterase, organophosphate-sensitive esterase), and acetylcholinesterase were localized in the developing embryo and in the young nymph of the large milkweed bug, Oncopeltus fasciatus (Dall.). The esterase complex varied qualitatively with embryonic development. Aromatic esterase occurred in the 3-day-old embryo, aromatic esterase and acetylcholine-esterase were found in the 4-day-old embryo, while all three esterases occurred in the 5-day-old embryo and in the young nymph. The distribution of each esterase remained fairly constant during embryonic development; aromatic esterase was located in many tissues and cells, aliesterase occurred in the pericardial cells, and acetylcholinesterase was found only in the neuropile of the nerve cord and brain. In the young nymph, the number of sites of aromatic esterase activity was reduced while additional sites of aliesterase occurred; acetylcholinesterase activity remained in the neuropile.

THE CUTICLE OF THE TWO-SPOTTED SPIDER MITE, TETRANYCHUS TELARIUS (LINNAEUS) (ACARINA: TETRANYCHIDAE)

The cuticle of T. telarius (L.) examined by light and electron microscopy and subjected to tests for chitin and lipids is shown to be a thin layer with a pattern of external ridges. It is about 1.25 microns thick measured in the troughs and twice that thickness measured at the ridges. The ridges average from 1 to 1.6 μ apart. There is no tectocuticle but an outside lipoid layer and a dark-staining non-chitinous epicuticular layer from 0.1 to 0.2 μ thick. A double-layered inner procuticle is present. The outer layer of the procuticle remains unstained in contrast to the dark-staining inner layer. The inside surface of the cuticle bears elevations or ridges opposite the external troughs. The epicuticle only is shed at molting. It bears the branched setae and over the eyes is striated, the ridges being about 0.14 microns apart. Either one or both layers of the procuticle contain chitin.