fingers as needed. A drop of glue should be placed on each end of
the plasticine model caterpillar. The plasticine model caterpillar
should be held on a twig or leaf petiole for a few seconds until
the glue bonds. Brightly colored plastic flagging can be tied to
the base of a plant with plasticine model caterpillars to aid in collecting them at the end of the experiment. We recommend placing the flagging at the base of the plant rather than next to the
caterpillar so that birds and other predators are not likely to associate the flagging with the caterpillar and either avoid or seek out
other flags. Each plasticine model caterpillar should be assigned a
number, which is written on the flagging with permanent marker
and linked to a data sheet. The data sheet should contain information
about the caterpillar location, height, plant type, or other information
needed to answer the students’ questions. Plasticine model caterpillars
should be left in situ for about a week before collection. Collected plasticine model caterpillars should be placed individually in a container or
bag that prevents additional marks and labeled so that they can be
linked to the data sheet. Most predation is readily visible on the caterpillars in the field, although magnifying glasses or dissection microscopes may be helpful. “Wounding” can be broadly classified as bird,
small mammal, or invertebrate predation, but finer characterization
( i.e., large or small bird) is not possible (Figure 2; Low et al., 2014).
Low et al. (2014) provides an excellent photographic collection of predation marks.
Analyzing & Understanding Results
Calculating the percentage of plasticine model caterpillars preyed on
by each group of predators provides insight into differences among
groups. Graphing data is a great way to visualize these patterns, and
we recommend the graph choice chart to help students decide on
graph type (Webber et al., 2014). These results and graph correspond
to questions 5–6 on the assessment (Appendix 1).
Interpreting these results requires students to look for patterns,
such as whether plasticine model caterpillars at one location or of one
color were preyed on more frequently than another. The patterns they
look for should match their research question and help assess whether
their hypothesis was supported by their data. The three predator
groups (birds, small mammals, and invertebrates) may respond differently, so each predator group should be assessed separately. When
writing their conclusion (question 7; Appendix 1), students should reference their results and think about why particular patterns occurred.
For example: “We saw more predation on green caterpillars than red
caterpillars in our experiment, which might be because predators
thought that red caterpillars were distasteful or toxic.”
As experiments often raise new questions and help students
learn what they can do differently, questions 8–9 (Appendix 1)
assess improvements and extensions of the experiment. Question 8
requires students to describe an improvement to their experiment.
Then, students apply what they have learned to a hypothetical continuation of this experiment by thinking of a new question, hypothesis, and way to test that question using plasticine model caterpillars.
After completing the experiment and assessment, students will have
participated in a complete research experience.
Figure 1. Plasticine model caterpillar (left) next to a real
notodontid caterpillar (right).
Figure 2. Imprints left on plasticine model caterpillars by birds
(top), invertebrates (middle), and small mammals (bottom).