Visit Your Local PBS Station PBS Home PBS Home Programs A-Z TV Schedules Watch Video Donate Shop PBS Search PBS
SAF Archives  search ask the scientists in the classroom cool science
Guide Index

Nasty Critters

All That Glitters

Looping the Loop

Dead Men's Tales

Model Planet

Viewer Challenge
in the classroom

THE WILD WEST: Nasty Critters

Begin your visit to the Wild West by tracking rattlers in the desert and hunting scorpions by the glow of a UV lamp. The scientists who pursue these two legendary villains of the desert aren't worried, though. Biologist Steve Beaupre knows how to handle rattlesnakes and even paints their rattlers. Ecologist Gary Polis knows that most scorpions are far more dangerous to each other than to humans. Through their work, the two scientists are learning more about these species and the desert ecosystem.

Curriculum Links
Activity 1: Build A Mobile
Activity 2: UV Detection
Did You Know?



sense organs,

toxic solutions


animal behavior,
reptiles, scorpions


electromagnetic spectrum,
UV light


What makes a scorpion unique? What are its distinguishing features? What other species are similar? Biologists classify living things to illustrate relationships among organisms; taxonomy is the branch of biology that deals with classification. For example, animals with jointed legs and a chitinous exoskeleton are classified as arthropods. By studying taxonomy and the characteristics of animals, you can find out more about the scorpion and its relatives.

Scorpions belong to the most successful group of land-adapted invertebrates, the arthropods (phylum = Arthropoda). As many as 930,000 species, mostly insects, are known to belong to this phylum (as many as six million species may exist; arthropods make up about 75 percent of Earth's known species).

Use your taxonomic research to build a mobile to help you visualize the relationships among living species.

  • yarn
  • index cards
  • small dowel
spider Procedure:
  1. Cut index cards in half (to save paper and achieve a better rotation on mobile). Write the phylum name (Arthropoda) on one card (this card will be at the top of the mobile). The card on the next level identifies a class within that phylum (e.g., Arachnida).

  2. On the lowest tier, illustrate four species from the class Arachnida (for example, representatives from four orders: a daddy longlegs, a tick, a spider and a scorpion). Include scientific names on the front side; supply additional taxonomic information such as subphylum, order, etc., on the reverse, as well as distinguishing characteristics.

  3. String the cards in a mobile to represent the taxonomic relationships of the animals illustrated. This mobile is only a partial representation of the classification scheme; you can expand it to represent two or more subphylums or classes; make it as complex as you wish. Note: you will need to consult a resource that contains detailed classification information.

  1. Name three animals closely related to the scorpion.

  2. Can you complete the taxonomic identification of a selected species of scorpion?

  3. Why do you think arthropods adapted so successfully to life on land? How might the scorpion's "nastiness" help it survive?

  4. How are scorpions different from insects?
  • Expand this mobile to illustrate other classes or subphylums.

  • Illustrate flash cards to study arthropods or some other group of animals. Draw a picture of the animal on one side and include classification information on the reverse.

  • What myths gave the constellation Scorpius and the class Arachnida their names?


snake A rattlesnake is classified as a pit viper, a family of snakes with highly developed sensory receptors called pit organs, located on each side of the head between its eye and nostril. These receptors detect warm-blooded prey hidden by vegetation or cloaked by the cover of darkness.

As you saw on FRONTIERS, the paired placement of pit organs on either side of the rattlesnake's head produces a three-dimensional sense of heat perception, similar to the sense of stereovision in people. This stereoscopic effect enhances the rattler's ability to detect areas of heat -- clues to prey and warmer areas (snakes are reptiles and must regulate their body temperature).

In the following activity, you'll experience how perception can be augmented when additional energy waves are exploited. In this case, you'll use UV radiation produced by a black light to excite fluorescent paint, causing it to glow.

  • black light
  • fluorescent paint (paint that glows when bathed in black light)
  • paint brush
  • small animal models (made from paper, cardboard or wood, or purchased from craft stores)


  1. Make several small mammals such as mice, rabbits or moles out of wood or paper and paint them with fluorescent paint.

  2. Place the animals in a large box or room that can be darkened. Partially obscure each animal with vegetation-like camouflage.

  3. Darken the room. Challenge other students to locate the "hidden" mammals.
  4. Position a black light overhead. Repeat the challenge.
  1. How did the black light help you locate the animals?
    (The black light made the painted animals glow, making them easier to locate.)
  2. What type of radiation did you observe?
    (Visible light)
  3. How is the black light's UV radiation like the infrared radiation of body heat?
    (Both are outside the optical window, rendering them invisible.)
  4. Why does UV light cause the scorpion's exoskeleton to glow?
    (A material in the exoskeleton absorbs visible light, then radiates UV light.)

  1. Compare and contrast your experience uncovering the UV targets with a snake's ability to detect warm-blooded prey.

  2. Infrared film captures images that include more of this heat-associated wavelength. Experiment taking photos with infrared film in the day and at night; have the film processed and compare photographs.

  3. If you have access to America Online, you can listen to a rattler. Go to the software libraries in the Computing area (Music & Sound Forum). Using the search icon, type in the keyword rattlesnake and download the file (sound sample). (On the Windows version, look under Mac software.)


  • The oldest scorpions known are fossils dating from the Silurian Period in the Paleozoic Era (c. 425 to 405 million years ago) and may have been among the first land animals.

  • The Chinese use dried scorpions to prepare a medicinal tea.

  • Scorpions form the largest biomass in the world's deserts.

  • Some Native American tribes believe that because it sheds its skin, the rattlesnake symbolizes special powers of healing and renewal.


Scientific American Frontiers
Fall 1990 to Spring 2000
Sponsored by GTE Corporation,
now a part of Verizon Communications Inc.