Sternum canal see sternal canal

sterols [Gr. stereos, solid] Alcohols of high molecular weight containing benzene-rings found in plants and animals.

sterrasters n. [Gr. sterrhos, solid; aster, star] (PORIF: Des-

mospongiae) Large centered, globular spicules with rays reduced to small projections from the spherical surface.

sterrula n. [Gr. sterrhos, solid] (CNID: Anthozoa) A solid free-swimming larva of Alcyonaria; stereoblastula.

stethidium n. [Gr. stethos, breast] 1. (ARTHRO: Chelicerata) In Acari, the nonsclerotized prodorsum. 2. (ARTHRO: Insecta) The thorax and its appendages.

stethosoma n. [Gr. stethos, breast; soma, body] (ARTHRO: Chelicerata) In Acari, that part of the body from the cir-cumcapitular furrow to the disjugal furrow; prosoma without the gnathosoma.

Stewart's organs (ECHINOD: Echinoidea) In cidaroids, coelomic pouches associated with Aristotle's lantern, functioning for interchange of gases.

stichic a. [Gr. stichos, row] Pertaining to a row parallel to the longitudinal axis.

stichocyte n. [Gr. stichos, row; kytos, container] (NEMATA: Adenophorea) An individual cell of a stichosome.

stichosome n. [Gr. stichos, row; soma, body] (NEMATA: Adenophorea) A longitudinal series of cells (stichocytes) that form the posterior esophageal glands.

sticklac n. [A.S. sticca, stick; Skr. laksa, lac] (ARTHRO: Insecta) Branches or twigs covered with the dried lac of scale insects. see lac.

stigma n.; pl. stigmata [Gr. stigma, mark] 1. A spiracle or breathing pore. 2. (ARTHRO: Chelicerata) In Acari, a sclerite surrounding a spiracle. 3. (ARTHRO: Insecta) a. A colored wing spot. see monostigmatous. b. In Odonata, a tick-ening of the wing membrane along the costal border near the apex. c. In Diptera, An apodeme at the base of the ventral surface of the postgenital lobe of female mosquitoes; basal median (longitudinal) apodeme; a sclerite surrounding a spiracle on a maggot. 4. (platy: Trematoda) In Schistosomatoidea, an operculum-like area of an eggshell through which the miracidium hatches.

stigmal vein (ARTHRO: Insecta) A short vein extending posteriorly from the costal margin of the wing; stigma.

stigmatal field (ARTHRO: Insecta) An area around the spiracles of larvae; spiracular disk; respiratory disk. see spiracular line

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