A Little Bit More
Usually, when we look at an animal’s defenses, we note those that are especially interesting, unusual, or impressive. The defense mechanism described in this unit, however, is not particularly impressive at all, but it is highly effective. If you’ve ever walked through a field of tall plants and saw insects feeding on the leaves, you may have been inclined to reach over and pick one up. Just as your hand got close to that insect, it simply rolled off the leaf and was gone – I know because this has happened to me many times.
Striped Cucumber Beetle
Scientists like to label things so they’re sure what they’re talking about and this behavior is no exception. This behavior has been labeled thanatosis (than –ah-TOE-sis) which is death-feigning (pretending to be dead), a behavior that is found in mammals, birds, reptiles, as well as, insects around the world. One aspect of this behavior that is known for animals that have been captured by predators, involves a reaction that instead of continuing to struggle, they simply go limp and appear dead. When a predator is no longer intent on trying to subdue a struggling prey item, it may relax its grip or attention and this may give the prey an opportunity to escape – at least this is the current thinking.
Of course, we humans can use our ability to think and plan a strategy and I soon learned to place a hand under the leaf BEFORE trying to pick an insect up. This way, if the insect rolls off the leaf, it simply falls right into my hand!
Activities
Science – Insect Defenses
Objectives: Clarify the defenses many insects use
Materials: None is necessary but a Field Guide may help
Here are some defense categories that insects use to defend themselves. I’ll give you the categories and one example and you and your students can see if you can come up with some other examples that fall under each one of these behaviors.
Chemical Defenses Bombardier Beetle releases a hot liquid
Mechanical Defense Caterpillar Killer Beetle can bite
Protective Coloration Giant Swallowtail Butterfly caterpillar looks like a bird dropping
Motor Defenses Dragonfly is an extremely swift flyer
Distasteful Monarch Butterfly caterpillar and adult
Key Concepts
Predator/Prey Relationships, Behavior and Regulation, Adaptations and Diversity
Questions
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