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Urticating Hair

Discussion in 'Tarantula Chat' started by mcluskyisms, Jul 22, 2010.

  1. mcluskyisms

    mcluskyisms Arachnoangel

    Just found an awesome write up on urticating hairs and decided it should be posted on here for people to read and understand just how amazing a defense mechanism these things really are!!!

    Urticating hairs

    Urticating hairs are one of the primary defense mechanisms used by some New World tarantulas and lepidopteran caterpillars. This term refers to the barbed hairs that cover the dorsal and posterior surface of the tarantula's abdomen or caterpillar. Many tarantula species will frequently kick hairs off their abdomens, directing them toward potential attackers. These hairs can embed themselves in the other animal's skin or eyes, thus inducing physical irritation. "Urtica" is Latin for "nettle".


    Urticating hairs do not appear at birth but form with each consecutive molt, outwardly presenting themselves around areas of more dark hairs on the upper back part of the abdomen of juveniles, widening from molt to molt, but in elder ages – merging with the main tone of abdominal coloration. Urticating hairs do not cover the entire opisthosoma and are distinct from abdominal hairs.


    There are six different types of urticating hair known in tarantulas (M. Overton, 2002). They are all different in shape and size.

    * Type I (0.2–0.6 mm)
    * Type II (0.5–1.5 mm)
    * Type III (0.3–1.2 mm)
    * Type IV (0.06–0.2 mm)
    * Type V
    * Type VI


    Each type of urticating hair is believed to target different enemies. Defined targets for some hair types are unknown.

    Type II is not kicked off by the tarantula. Direct contact is necessary to penetrate an attacker. Tarantulas from the genera "Avicularia", "Pachistopelma" and "Iridopelma" possess Type II hairs. (Toni Hoover, 1997)

    Type III
    urticating hairs are most efficient for defence against vertebrates and invertebrates.

    Types III and IV are the most irritant to mammalian predators.

    Types I, II, III and IV urticating hairs can be found in the subfamilies Avicularinae and Theraphosinae.

    Type I and III
    urticating hairs are representative on "Lasiodora" and "Acanthoscurria", excluding "Grammostola" (exhibits types III and IV).

    Type III
    urticating hair is typically found on the species of "Theraphosa spp.", "Nhandu spp.", "Megaphoboema spp.", "Sericopelma spp.", "Eupalaestrus spp.", "Proshapalopus spp.", "Brachypelma spp.", "Cyrtopholis spp.", "Iracema spp." and other genera of subfamily Theraphosinae (Rick West, 2002).

    Type V urticating hair is typical of the species of genus "Ephebopus". As mentioned earlier they are located on the pedipalps. They are much shorter and lighter in contrast with other types of urticating hair. These are easily thrown by the spider into the air (Marshal and Uetz, 1990).

    Type VI urticating hair is found in the genus "Hemirrhagus" (F. Perez-Miles, 1998,)
    According to Vellard (1936) and Buecherl (1951), genera with the most urticating hairs are "Lasiodora", "Grammostola" and "Acanthoscurria".

    Defensive behavior utilizing urticating hairs

    New World tarantulas will at the moment of danger, turn toward the attacker and briskly rub their hind legs against the opisthosoma throwing the urticating hairs in the direction of the enemy.
    The latest studies suggest urticating hairs from tarantulas present not just a mechanical but a chemical influence on the skin and mucous membranes.

    The cloud of small hairs will get into the mucous membrane of small mammals and cause edema, which can be fatal.
    Reaction and the degree of irritation to a defensive urticating hair barrage can vary tremendously, based on the species in question.
    Some, such as those of the Chilean rose hair ("Grammastola rosea") and the pinktoe tarantula ("Avicularia avicularia"), are fairly mild and innocuous to humans.

    Others, such as those of the Brazilian giant white knee tarantula ("Acanthoscurria geniculata"), are moderately irritating.
    Still others, such as the Goliath Birdeater ("Theraphosa blondi"), are far more severe. These hairs can result in painful rashes, and have been likened to sharp shards of fiberglass.
    After a defensive maneuver, an urticating hair lobbing tarantula will have a bald spot on its abdominal region.

    Families of Lepidoptera with urticating hairs

    There are species with urticating hairs in at least eleven Lepidopteran families: the Arctiidae (tiger moths), Anthelidae (lappet moths), Bombycidae, Eupterotidae (bag shelter moths), Lasiocampidae, Limacodidae, Lymantriidae (tussock moths), Megalopygidae, Noctuidae, Notodontidae (processionary caterpillars), Nymphalidae, and Saturniidae (Matheson 1950, Riley and Johannsen 1938, Roth and Eisner 1962, Wirtz 1984). Some adults may also have urticating scales.

    Human reactions to urticating hair contact

    In humans a defensive cloud of urticating hairs can cause allergic skin reactions which can manifest itself as inflammation, rash and itching. The reactions can last for several hours or days. A chemical influence upon the skin and mucous membranes explains the different reactions of people to urticating hairs (Rick West, 2002).
    It seems likely the hairs cause an accumulative reaction in people.
    A solution of 2–2.5% hydrocortisone cream applied to the affected area may help relieve the symptoms.
    A more serious consequence is urticating hair in the eyes. In this case it is necessary to immediately wash the eye thoroughly with copious amounts of cold water and see an ophthalmologist.

    Urticating hair as territorial markings

    Urticating hair is not just thrown at an enemy as a first line defence. It is also used as an indication of territory. It can be found on and around the burrow entrance and in webbing for protection (for example, some of Theraphosinae subfamily species include these hairs in cocoon silk).
    Urticating hair can also be found protecting tarantula egg sacs ("Avicularia" spp. and "Theraphosa blondi" respectively). This is thought to discourage fly larvae from consuming their eggs and young.

    Matheson R. 1950. Medical Entomology. (2nd ed.). Comstock Publications, Ithaca, New York. 612 p.

    Riley WA, Johannsen OA. 1938. Medical Entomology; a Survey of Insects and Allied Forms Which Affect the Health of Man and Animals. McGraw-Hill, New York. 483 p.

    Roth LM, Eisner T. 1962. Chemical defenses of arthropods. Annual Review of Entomology 7: 107-136.

    Wirtz RA. 1984. Allergic and toxic reactions to non-stinging arthropods. Annual Review of Entomology 29: 47-69.
    • Like Like x 1
  2. thanks for this - an article i didn't know i wanted to read until i read it, heh heh heh
  3. Scoolman

    Scoolman Arachnolord

    Nice job. I have read this information in different articles, but it is nice to have it all together in one place.
  4. mcluskyisms

    mcluskyisms Arachnoangel

    Cheers :)

    I found it interesting too so I wrote it up
  5. Scoolman

    Scoolman Arachnolord

    Very well done. :worship:
    This should be stickied under "Questions and Discussions".
  6. mcluskyisms

    mcluskyisms Arachnoangel

    I just tinkered with the original mate, the work belongs to the authors

    They deserve the gratitude :)
  7. Scoolman

    Scoolman Arachnolord

    True, but you compiled the information; and gave proper credit. That's how research writing works.
  8. Miss Bianca

    Miss Bianca Arachnoprince

    Agreed, in the scientific discussion section. Far more instructive than chat.
    • Agree Agree x 1
  9. +1 :clap: Wow! Your condensation certainly appears stickyworthy to me. Doesn't everyone agree!?

  10. Endagr8

    Endagr8 Arachnoangel

  11. Scoolman

    Scoolman Arachnolord

  12. crawltech

    crawltech Arachnoprince

    Sticky as honey!.....very informative!
  13. mcluskyisms

    mcluskyisms Arachnoangel

    Cheers guys, I just want to say again that I didn't actually write the information, which is stated at on the start of it, all I did was paste a picture I found relative to the information into it and tidied it up slightly. Just wanted to post it for educational purposes as I found it a good read.

  14. gromgrom

    gromgrom Arachnoprince

    +1 to sticky this topic :)

    i recently finally, got kicked at, and got my LP's butthair all over my hands. itched like poison ivy for about 24 hours, then just pink spots.
  15. Kathy

    Kathy Arachnoangel

    I don't worry about myself, but I always worry about my cat getting it into his lungs.......since it can kill small mammals. Interesting read and picture. I enjoyed it, thanks.!
  16. mcluskyisms

    mcluskyisms Arachnoangel

    Yeah, I always find it interesting how a tarantulas venom can kill a mouse or a rat a lot easier than it can harm a human, obviously we are a lot bigger but another theory is what would be more a natural predator to tarantulas would be....

    ie what mammals would be able to get into there burrows to attack them, so has their venom evolved itself into being more astute at killing smaller mammals.....?