Academic journal article The American Biology Teacher

Using Dragonflies as Common, Flexible & Charismatic Subjects for Teaching the Scientific Process

Academic journal article The American Biology Teacher

Using Dragonflies as Common, Flexible & Charismatic Subjects for Teaching the Scientific Process

Article excerpt

Biology laboratories are usually designed around convenient and available subjects. For example, for animal laboratories Daphnia magna, Drosophila melanogaster, frogs, rats, and mice are common animals that are relatively easy to obtain, relatively cheap, and consequently lend themselves well to laboratory experimentation. On many campuses, however, a body of water exists-either in the form of a creek or small pond-and this water attracts numerous animals that have tremendous potential as subjects for teaching. Chief among these animals are the dragonflies and damselflies. Dragonflies and damselflies occupy different suborders of the insect order Odonata, and, although both make great subjects for teaching, I focus primarily on dragonflies in this article. Below I explain why dragonflies make great subjects, give some practical advice for using them in your teaching, and then provide a few specific examples for how I have used them in my classes. My hope is that by giving a little background information and a bit of an admittedly biased push in their direction, dragonflies will become more appreciated and more utilized in science teaching.

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Dragonflies as Teaching Subjects

Dragonflies are ideal teaching and research subjects for a number of reasons. First, they are common and relatively easy to work with. Students can approach them closely, watch them, and capture, mark, and release them. Dragonfly larvae are aquatic, easy to capture using aquatic nets, and seem content to go about their business quite readily either in the field or in the lab. For instance, when held in jars after capture, the larvae behave normally and will try to eat other invertebrates in the jar. Adults are a bit more wary, yet if students avoid sudden movements or approaches, they can get within inches of many common species. Capture requires no more exotic equipment than either aerial (for adults) or aquatic (for larvae) nets, and adults can be quickly and cheaply marked with permanent marking pens or with white correction fluid. Moreover, adults can be used in many projects without capture. In addition, males and females of most common species can be distinguished from a distance.

Second, dragonflies are very charismatic and are effective ambassadors of the insect/invertebrate world. Probably only butterflies rival dragonflies as the most popular invertebrate in jewelry and clothing, and dragonflies provide interesting links between the natural world and art and poetry. For example, dragonflies have long played an important role in Haiku, as a brief Internet search for "Haiku" and "dragonfly" will demonstrate. Also, in my experience, once students acquire just a little information about dragonflies, only praying mantises (another fascinating insect predator) rival dragonflies for intrinsic "insect interest." Because of their rising popularity with the general public, dragonfly field guides have become more common and more "user-friendly," in the sense that many are now designed with the layperson in mind. Consequently, identifying the common dragonflies and, to a lesser extent, the damselflies, is easier than ever.

Third, dragonflies have a variety of interesting ecological roles and behavior in both the larval and adult stages. Dragonfly larvae are dominant invertebrate predators in many aquatic habitats and can help shape communities. Larvae capture prey by shooting out a modified lower mandible and grabbing prey, and larvae of larger species may eat small vertebrates (e.g., amphibian larvae and fish) as well as invertebrates. Dragonfly larvae move either by crawling or by jet propulsion, using water forcibly expelled out their anus. Adults are also predaceous, and males of many of the most common species are territorial, exhibiting a variety of conspicuous aggressive and mating behaviors. Their chases and fights can make quite an impression, especially once the students figure out what they are observing. …

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