What is "steel trap"

Steel \Steel\ (st[=e]l), n. [AS. st[=e]l, st[=y]l, st[=y]le; akin to D. staal, G. stahl, OHG. stahal, Icel. st[=a]l, Dan. staal, Sw. st[*a]l, Old Prussian stakla.]

1. (Metal) A variety of iron intermediate in composition and properties between wrought iron and cast iron (containing between one half of one per cent and one and a half per cent of carbon), and consisting of an alloy of iron with an iron carbide. Steel, unlike wrought iron, can be tempered, and retains magnetism. Its malleability decreases, and fusibility increases, with an increase in carbon.

2. An instrument or implement made of steel; as:

   1. A weapon, as a sword, dagger, etc. ``Brave Macbeth . . . with his brandished steel.''
      --Shak.

      While doubting thus he stood, Received the steel bathed in his brother's blood.
      --Dryden.

   2. An instrument of steel (usually a round rod) for sharpening knives.

   3. A piece of steel for striking sparks from flint.

3. Fig.: Anything of extreme hardness; that which is characterized by sternness or rigor. ``Heads of steel.''
   --Johnson. ``Manhood's heart of steel.''
   --Byron.

4. (Med.) A chalybeate medicine. --Dunglison. Note: Steel is often used in the formation of compounds, generally of obvious meaning; as, steel-clad, steel-girt, steel-hearted, steel-plated, steel-pointed, etc. Bessemer steel (Metal.) See in the Vocabulary. Blister steel. (Metal.) See under Blister. Cast steel (Metal.), a fine variety of steel, originally made by smelting blister or cementation steel; hence, ordinarily, steel of any process of production when remelted and cast. Chrome steel, Chromium steel (Metal.), a hard, tenacious variety containing a little chromium, and somewhat resembling tungsten steel. Mild steel (Metal.), a kind of steel having a lower proportion of carbon than ordinary steel, rendering it softer and more malleable. Puddled steel (Metal.), a variety of steel produced from cast iron by the puddling process. Steel duck (Zo["o]l.), the goosander, or merganser. [Prov. Eng.] Steel mill.

   1. (Firearms) See Wheel lock, under Wheel.

   2. A mill which has steel grinding surfaces.

   3. A mill where steel is manufactured.

      Steel trap, a trap for catching wild animals. It consists of two iron jaws, which close by means of a powerful steel spring when the animal disturbs the catch, or tongue, by which they are kept open.

      Steel wine, wine, usually sherry, in which steel filings have been placed for a considerable time, -- used as a medicine.

      Tincture of steel (Med.), an alcoholic solution of the chloride of iron.

      Tungsten steel (Metal.), a variety of steel containing a small amount of tungsten, and noted for its tenacity and hardness, as well as for its malleability and tempering qualities. It is also noted for its magnetic properties.

n. an acute intelligence (an analogy based on the well known sharpness of steel traps); "he's as sharp as a steel trap"; "a mind like a steel trap"

Steel trap (sometimes written "steel-trap" or "steeltrap") is an informal term in the study of comparative plant physiology of the carnivorous plants. "Steel trap", more particularly "active steel trap", refers to prey capture devices such as occur in some members of the family Droseraceae, and in particular in the genera Dionaea ("Venus flytrap") and Aldrovanda ("waterwheel"). The term apparently originated with the author Francis Ernest Lloyd in 1942, in which he adopted the overly general term "steel trap" rather than say, " gin trap" or a more adjectival form, for devices such as the lobed trap leaves of Dionaea.

The distinctive attributes of "steel trap" devices are that:

• they are active, capturing prey with positive movements, not relying on mere stickiness, hooks, pitfalls or the like;
• prey capturing activity occurs only in response to specific tactile stimuli — prey making contact with sensory bristles;
• the action is a thigmonastic, stereotyped, rapid movement (often completed in well under one second).

When the term "steel trap" originally was published, it apparently referred in part to the shape of the trap mechanism, but in terms of their functional significance rather than their shape, the associated concepts listed could apply equally well to the bladder traps of Utricularia and to the more recently described action of the Australian sundew species Drosera glanduligera. Those species also trap actively, in response to tactile stimuli, using a rapid thigmonastic response.

At all events, the "active steel trap" mechanism differs in one or more of these respects from trap mechanisms in other members of the family Droseraceae. It also differs from other passive trapping mechanisms such as those of the pitfall traps of pitcher plants. The genus Drosophyllum for example, uses the "passive flypaper" mechanism, in which prey in contact with the sticky fluid on the bristles of the leaves simply get more tangled as they struggle.

This "passive flypaper" mechanism of Drosophyllum differs in turn from the "active flypaper" trap of the related sundew genus Drosera. The adhesive-bearing bristles or "tentacles" of most Drosera species nastically bend inwards, trapping the struggling insect, and commencing the process of digestion. These movements are slow and very different from the steel trap action.

Drosera glanduligera has a mechanism in some ways different from the typical "active flypaper" of most Drosera species. Its sticky tentacles grow only in the flat area of its round, peltate leaves; around the margin of the leaf there are long, jointed tentacles that snap inwards when stimulated, catapulting prey inward to succumb to the sticky tentacles in the usual manner.