CISEO: Enforcers Lesson Plan

Activity 1: Observation of a predator-prey interaction

In this activity, students will be observing an insect predator attacking its prey. This will introduce students to interactions and behaviors that will lead them to ask their own questions and design an experiment based on that question. They become oriented to techniques and materials that they will be using in subsequent activities.

Class Time Required
10-15 minutes preparation one day prior to lesson
approximately 1 hour

Materials Needed
Per group:

1-3 Petri dish habitats (see Petri Dish Habitat instructions)
distilled water, 1 gallon
eye dropper
aphid infested host plant leaves, 1-2 for each dish
soft forceps, eyelash brushes (see Eyelash Brush instructions), and/or small paint brushes
dissecting microscope and/or hand lenses
clock with second hand or stop watch
live aphid predators (ladybird beetles-adults and/or larvae, green lacewing larvae, big-eyed bugs)

Preparation
The day before introducing the lesson, either prepare Petri dish habitats yourself or have your students make them (see Petri Dish Habitat instructions). On the day of the lesson place an aphid infested leaf in each dish. Have containers of each of the predators available and ready for students to transfer into their Petri dishes. Provide tools for handling the predators such as soft forceps, small paint brushes or eyelash brushes (see Eyelash Brush instructions.)

Insect Note

Predators will perform better when they are hungry. You may want to starve the predators for 1-2 days before introducing them to the aphids.

Observe Pradator-Prey Interactions
Distribute a predator and stop watch to each lab group. Have teams use eyelash brushes to gently transfer the predator into a prepared Petri dish. Allow students to observe predator-prey interactions for up to ten minutes. Listen as students offer unsolicited descriptions of the physical characteristics and behavior of each predator. Encourage students to be specific about each predator’s use of mouth parts, legs, and antennae. Have students record the predator and prey behaviors at regular intervals especially noting the time it takes for each predator to find and devour its prey. Encourage students to use their journals to make drawings, notes, and write questions as they observe the insects.

Ask students to share their observations and questions. Encourage them to give evidence for their answers. Facilitate the discussion by asking the following:

What behaviors do you first observe in the predator? (searching behavior, antennal movements)

What other behaviors do you notice? (grooming, extension of mouthparts, feeding)

What might be possible explanations of those behaviors? (antennae – which are used to smell the surrounding environment – help the predator locate the prey, the piercing-sucking mouthparts of some predators need to be extended in order to feed)

What does the aphid do when the predator approaches? (crawls away, kicks)

How does the predator capture and hold its prey? (uses it forelegs to hold the prey, may have some paralytic ingredient in its saliva to paralyze prey)

If time allows, have the students repeat their observations with a different predator. You may want students to report their observations in a chart form such as the example shown below:

Location/Behavior

Time	Predator 1	Predator 2	Predator 3	Prey
Minute 1
Minute 3
Minute 5
Minute 7
Minute 10
Next 10 minutes

Facilitate further discussion by asking the following
How long did it take for the different predators to find, capture and eat their prey? (some predators may move more slowly, be smaller, or have poorer vision causing them to take longer to find the prey)

Why might it take a predator longer to eat its prey? (different mouthparts are more efficient for eating different types of prey)

How are the behaviors of the different predators similar or different? (many predators have similar searching behaviors)

Insect Note

Adult ladybird beetles are less likely to eat aphids in the late summer or early fall. This is due to the physiological and behavioral changes that the beetles undergo to survive the winter (diapause.)

Insect Note

All arthropods, including insects are ectotherms, and will behave more normally when their environment is warm (ideally around 80°F.)

Ode to a Reluctant Predator
Ladybird, ladybird, why must you roam
While aphids around you siphon the phloem?
Maxillae and mandibles, your grasping jaws,
Serve me unwell while in diapause.