Ballistic defecation: hiding, not hygiene. (Zoology).Evading predators may be the big factor driving certain caterpillars to shoot their waste pellets great distances. Caterpillars of the silver-spotted skipper The Silver-spotted Skipper (Hesperia comma) is a butterfly of the Hesperiidae family. It is known as the Common Branded Skipper or Holarctic Grass Skipper in North America, where the butterfly Epargyreus clarus (Epargyreus clarus) can fire their feces as far as 153 centimeters, reports Martha R. Weiss of Georgetown University Georgetown University, in the Georgetown section of Washington, D.C.; Jesuit; coeducational; founded 1789 by John Carroll, chartered 1815, inc. 1844. Its law and medical schools are noteworthy, and its archives are especially rich in letters and manuscripts by and in Washington, D.C. Accounts from other researchers record tales of shots by caterpillars of other species of up to a meter. To compare three theories of what evolutionary force drove the development of such firepower, Weiss set up challenges for groups of silver-spotted skippers, a species in which a caterpillar builds a series of shelters out of curled leaves and silk lines as it grows. One hypothesis proposed that blasting the waste far away lowers the risk of disease. To test this, Weiss let feces build up in little containers housing some of her caterpillars. As they developed, she found no obvious difference between them and caterpillars in pristine containers. Another hypothesis proposed that the waste ejection ejection /ejec·tion/ (e-jek´shun) 1. the act of casting out or the state of being cast out, as of excretions, secretions, or other bodily fluids. 2. something cast out. 3. keeps sewage buildup from crowding the caterpillars out of their homes. Yet when Weiss forced caterpillars to build new shelters more often than normal, she saw a significant drop in caterpillar welfare only in the most extreme version of this test--when evicted caterpillars constructed 32 shelters, instead of the usual 9, as they grew and developed. In contrast, Weiss found support for the hypothesis that waste draws a predatory wasp to the caterpillars. For example, wasps killed 14 out of 17 caterpillars on leaves where she had put waste pellets but only 3 of 17 caterpillars on leaves she had adorned a·dorn tr.v. a·dorned, a·dorn·ing, a·dorns 1. To lend beauty to: "the pale mimosas that adorned the favorite promenade" Ronald Firbank. 2. with glass beads. In the April Ecology Letters Ecology Letters is a peer-reviewed scientific journal published on behalf of the Centre National de la Recherche Scientifique by Blackwell Publishing. Within 9 years, the journal attained an Impact Factor of 7. , Weiss reports that predators are the most likely force behind pellet ballistics ballistics (bəlĭs`tĭks), science of projectiles. Interior ballistics deals with the propulsion and the motion of a projectile within a gun or firing device. .--S.M. |
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