Project Skill: Learning about beneficial insects Life Skills: Learning to learn
Planning and organizing
Applying science and technology
What To Do: Collect and prepare a display of beneficial insects
Natural control by beneficial insects (unaided by human involvement) occurs all the time. If there was nothing to prevent plant-feeding insects from surviving and reproducing, they would increase in numbers, and eat up every host plant until there was no longer anything left to eat. Obviously that doesn't happen, since there are lots of plants around us. The populations of all insects, including pests, are regulated by a variety of natural environmental factors, including weather and other organisms. Natural enemies are organisms that kill individuals of another species.
Beneficial natural enemies that control pest insects belong to 4 broad groups: predators, parasites, nematodes, and pathogens (diseases). Beneficial insects are either predators or parasites. Predator insects are usually mobile, and each kills and eats many pests ("prey") during its life. Common predators include lady beetles and green lacewings that feed on aphids, and spined soldier bugs and ground beetles that feed on soft-bodied insects, such as caterpillars. A parasite eats only a single pest (its "host") during its development, and often lives within the body of the pest as an immature, consuming the pest from the inside. As a winged adult it searches for more hosts for its offspring. Common parasites include tachinid flies and various stingless wasps, often developing in caterpillars. These insects are usually more choosy about their host than predators are about their prey, often selecting only one species of insect to parasitize.
Natural control is an important but often overlooked form of pest control. Although natural control is extremely important in keeping pest numbers below damaging levels, some pests still get too numerous by people's standards. Biological or other forms of control (such as pesticides) may be used to manage these pests. Biological control is the intentional manipulation of natural enemies to limit pest populations.
Level 1: Collect and preserve adult parasites and predators to create a display of common beneficial insects in your area.
Level 2: Add text describing host/prey for each insect and the general habitat it is normally found in.
Level 3: Prepare life cycle drawings to accompany the text. Indicate which stages feed on the host.
Locate suitable collecting sites and plan collecting trips. Backyards can be good collection sites (unless they've been sprayed with pesticides). Parasitic wasps feed on nectar, so they can be collected as they visit flowers such as sweet alyssum, Queen Anne's lace, and buckwheat. Lots of beneficial insects can be found in alfalfa fields. Look under mulch or in compost piles for ground-dwelling insects. The vegetation along a stream or even weedy roadsides can be good habitats for insects.
Find some books for identifying the preserved specimens (see RESOURCES; also check your local bookstore or nature store).
Collect adult insects from a variety of habitats. Put the captured insects in a killing jar or leave them in a tightly sealed jar in the freezer for a few days.
Pin, mount, spread or otherwise preserve the specimens. (Refer to Discovering the World of Insects, University of Wisconsin-Extension Publication 4-H 338 or equivalent.)
Try to determine the order and family (major classification groups) of each insect. (A good reference book on insects will be necessary to identify some of the insects.) Label each insect with its scientific family name. Indicate which are predators and which are parasites.
Prepare a display of the identified insects.
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