Science on a Shoestring
Insects can be used to explore biodiversity, collect and analyze data, and engage in inquiry. They can be collected with minimal expense and preparation and then used by students for skill-building in identification, graphing, and experimental design, depending on the instructor’s goals. The vast diversity of insect species is wondrous. Insects evolved from crustaceans more than 400 million years ago, long before the dinosaurs. They were the first organisms to develop the ability to fly. Today there are over 1,000,000 species of insects worldwide with every color and lifestyle imaginable.
The bowl trap methodology described in this article was used by the author while studying pollinator diversity in Greenland with PolarTREC (Climate Change and Pollinators in the Arctic 2016). It is a simple, effective means of introducing students to field work and environmental education, as well as generating authentic data. Groups of two to four students work well for these activities, which provide students opportunities to practice basic scientific skills using authentic, student-generated data. Moreover, the activities establish the concept of biodiversity, providing a foundation for biology and ecology lessons throughout the remainder of the academic year.
A bowl of soapy water is a simple, yet effective trap for insects. Normally, small insects can safely land on the surface of water because the water molecules are attracted to one another by the force of cohesion. This force creates a skin on the water that small insects can walk upon. However, adding soap to a bowl of water disrupts the cohesive force, allowing insects to sink and become trapped (Figure 1).
For this activity, you will set out plastic, eight-ounce bowls of slightly soapy water as traps. You can place bowls 24 to 48 hours in advance of a class period, or students can take a few minutes of class time to set the bowls themselves. Check the weather forecast; bowls should be used when precipitation is not anticipated. Place the bowls in desired location(s), depending on the school campus. Possibilities include landscaped beds, lawns, wooded areas, meadow areas, ditch areas, and pond banks. Dumpster locations are not recommended based on experience; these bowls tend to be upended by animals that visit the dumpsters. (It is possible that some bowls will be lost due to wind, mowing, animal visits, or humans cleaning them up. It can be emphasized to students that this is one of the hazards of field work; it is important to try to anticipate problems of this type.)
Students can be given an opportunity to generate questions about collection locations, habitats, and even color. Either prior to the insect identification activity or afterward, once students understand the nature of the bowls, they can plan their own investigations and place their bowls in their preferred location (see below) after they have identified a question and written a hypothesis. Some possible questions include: What is the variety of habitats that we can identify on our own campus? Will we find more insects in a lawn or a landscaped bed? Will we find more insects in a riparian location (near a ditch, pond, or stream) or a drier location? Will we find greater diversity in one or another location? If our bowls are different colors, will insects prefer certain colors?
Students can use identification resources to document and compare diversity based on their findings by counting the number of insects or the number of insect families. Identifying the insects takes students some time, as they have not usually inspected insects closely before. Magnifying glasses and tweezers are useful tools. It is reasonable to expect that collecting the bowls and identifying one or more families will occupy a 40-minute class period. Using the collected insects, have students identify them using print resources or an online taxonomic key such as the one at KnowYourInsects.org. This site provides a dichotomous key, presenting a pair of questions on each page, letting students click each answer and taking them to more finely defined questions as they progress; ultimately, students will key an insect to a taxonomic family. In this way, students have the opportunity to sample the vast and diverse class, Insecta. An alternative method of identification is to use the iNaturalist app to identify the insects (see Resources). However, it bypasses the steps that scientists use in identifying organisms and doesn’t help students understand the nature of a dichotomous key. Through the identification process, students come to appreciate the diversity of life that surrounds them without their really having paid attention to it prior to their investigation. For most students their initial “Ewwww!” reaction transforms to one of curiosity pretty rapidly; of course, some students will continue to refuse to touch or engage with the insects, letting other members of their lab groups do the handling.
The data can be placed in a collated class spreadsheet to calculate averages for particular locations or bowl colors. Students can make inferences about their observations, and these form the basis of small-group or full-class discussions. Students may observe that there is more diversity in certain habitats than other locations. For example, there is often more diversity in a riparian location than in others. Ask students to speculate on why this might be. They may observe that there is more diversity in a naturalized area than in a lawn or landscaped area; ask students to speculate on the reasons.
Students may observe that certain insects appear to prefer certain colored bowls. (For example, in our experience, insects prefer white, yellow, and pink bowls to blue and green ones. In order to investigate color, bowls were painted with inexpensive acrylic paints.) Some research may indicate the preferences that the insects have for certain flowers based on color, shape, or scent. Students may also work individually or in groups to learn about the behavior and/or the evolution of one of their samples. Possible products include: a presentation about their insect’s habitat, a representative food web, an explanation of insect reproduction, a family tree for insect relationships, or a cladogram showing insect evolution.
There are numerous opportunities to assess students’ basic science skills, whether the instructor plans to grade these activities or use them as formative classroom experiences.
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Schoeffler A. 2016. Climate change and pollinators in the Arctic 2016.
Insect identification key—