Arachnid a (araknida)

pl. [NL., (a) In Lamarck's and Latreille's systems of cla ification, one of three cla es into which the Linnean Insect a were divided, the other two being Crustacea and Insect a; primarily divided into Pulmonaria and Trachea ria. (b) In Latreille's system, the second cla of articulated animals with articulated legs, apterous and ametabolous. It was divided into two orders, Pulmonaria and Trachea ria, the former containing the spiders and scorpions, the latter the false scorpions, harvestmen, and mites. (c) A cla of the phylum Arthropod a, including the spiders, scorpions, false scorpions, harvest ment and mites, with or without the They are apterous, ametabolous, articulate animals, with articulated legs. They are decephalized by the blending of the head with the thorax as a cephalothorax, normally bearing 8 legs, and never more; the antennæ are trans formed into chele when present; the abdomen is usually distinct but not segmented, or if segmented is not distinctly separated from the cephalothorax, and does not bear limbs, the appendages being in the higher forms transformed into spinnerets; the eyes are simple and gen erally more than two in number; the respiratory apparatus is pulmonary or tracheal, or compounded of these two IMG:content-1043.png:[blocks in formation] um), n.; pl. arachnid i a (-a). [NL., gan of the Araneid a, or true spiders; the glandular ap -inæ.] A subfamily of Aradida , having a comparatively long rostrum, the sternum grooved, the end of the abdomen with a thin cleft and Spy lobate margin, and the head with an angular proce exterior to the antenne. It is a large group, generally distributed in America from the arctic regions to the tropics. Two Arachnidial Mammillæ, or Spinner paratus by which the silky threads forming cobweb are ets (Sp1, Sp2) of a Spi der ( Mygale camen secreted and spun out. Numtaria). berle minute glands, provided with separate ducts, secrete the viscid material which hardens into silk when exposed to the air. The glands have been divided into five kinds: aciniform, ampul late, aggregate, tubuliform, and tuberous. Their ducts enter the arach nidial mammillæ, and discharge through orifices in the arachnidial papillæ.