Spiders - Lesson 3: Spiders Catch Prey
ACTIVITY: Spider Venom
Before performing this experiment the students discuss snakes having a poison
similar to spider's venom. Discuss ways to avoid danger of being bitten by
spiders. After the discussion, the students perform the spider's venom
experiment (sugar cubes and water); use pictures of/or dead black widows or brown
recluse spiders.
Objectives
Students observe a simulation of the effect of a spider's venom on its prey.
Materials
One styrofoam cup per group
One sugar cube per group
Very warm water
Procedures
- Give each group a cup with several sugar cubes in the bottom. Explain
that cubes are like the inside of an insect's body -- hard!
- Have children pour a few drops of water onto the cubes. What happens?
The water dissolves the sugar cubes just as the spider's venom dissolves the
insect's body when the spider spreads venom into the insect's body. Because a
spider can turn its food to liquid, it can eat without chewing!
- Discuss how people's diets would change if we didn't have teeth.
Discussion
Because the spider can only digest fluid food, predigestion must take place
outside the spider's body. Some people believe that spiders suck blood; this
is not correct. Spiders inflict a wound with their fangs and, through the wound,
inject digestive enzymes into the wound to liquefy the tissues of their prey.
Then the spider pumps the insect dry, leaving nothing but an empty shell
behind.
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