Biology teachers, and most science teachers in general, are constantly looking for cost-effective, "hands-on" experiences through which students can interact with concrete examples of the concepts and procedures being taught. Lepidopterans, especially when the species are living and attractive, can provide just such experiences in the classroom. You can use living lepidopterans to show, for example, complete metamorphosis, adult insect morphology, and courtship behavior. You can also study the relationships between lepidopteran species and specific foodplants. In addition, students can simply appreciate lepidopterans for their living beauty (Fig. 1).
Lepidopterans belong to the Insecta, a huge class of arthropodan invertebrates. Commonly called moths and butterflies, lepidopterans are characterized by two pairs of broad, membranous wings covered with very fine scales, which are often brightly colored.
Lepidopterans show complete metamorphosis; that is, they go through distinct egg, larval, pupal, and adult stages. Their larvae, called caterpillars, have chewing mouthparts and feed chiefly on plants. The lepidopteran inactive stage, called a pupa or chrysalis, may or may not be surrounded by a cocoon. The adults normally have a tubular proboscis for sucking liquids, especially flower nectar.
Female lepidopterans use chemicals, called pheromones, to attract males for mating. Copulation can last from just a few minutes to 10 to 12 hours (Fig. 2) depending on species.
In moths, ovipositing (or egg-laying) usually occurs immediately after mating. Depending on the species (saturniids work especially well), you can induce ovipositing; placing a female moth in a large paper bag with a few fresh leaves of the larval foodplant will usually induce the female to lay 100 to 300 eggs.
With butterflies, it is more difficult to stimulate ovipositing. The combination of sunlight (a sun lamp can be used) plus live plants (or sprigs of the larva's foodplant) - will usually induce a mated female to oviposit. Make a mesh cage the same height as the foodplant it is to contain. The female's feet touch the foodplant as she walks back and forth on the underside of the top of the cage. Butterflies have chemical receptors on their feet, and the constanttouching of the foodplant often helps tremendously in stimulating the ovipositing response.
All things considered, the purchasing of living material in the pupal (cocoon or crysalis) stage is the most practical solution to obtaining lepidopterans. Purchased pupae can be easily stored under normal refrigeration.Adults can be induced to emerge in three to three and one-half weeks by moistening them and maintaining them at room temperature in a small cage or covered aquarium. If you use a covered aquarium, place some type of textured material on its sides. Cheesecloth or paper toweling is recommended. This allows the emerging adults to climb and cling to expand and dry their wings. Otherwise, deformed adults usually occur.
For example, the complete life cycle can be followed on a day-to-day basis. The changes that occur from stage to stage - egg (Fig. 3) to larva (Fig. 4) to pupa (Fig. 5) to adult should be recorded in a diary. The diary should include dates, procedures, temperatures, behavior, and any significant structural changes that occur. Depending on the age and background of the students, this can be done as a class project or as individualized exercises that allow each student to learn as much as he or she is willing to do.The diary material then can be finalized into individual science reports explaining all the observations, or the class project can be written up and posted as a wall display.
Individual stages of the life cycle can also be examined in detail. Again, this can be done as a class project or as individualized experiments. Use a dirt-filled ant farm with two glass sides for a subterranean chamber. The class can study specific behavior - like ovipositing and mating, the spinning of a cocoon around the pupa, or the molting of a silk-cradled chrysalis. Adult specimens can be killed and observed through stereomicroscopy for both insect and lepidopteran characteristics. Adults can also be released once they have emerged and are dry. Many students find the releasing of indigenous species to be a very exciting and a rewarding end to the hard work of rearing the specimen.
Sideline experiments could also be done in seed germination and growing flowering plants. This would allow students to experience and learn about plant growth; the effects of light, fertilizer, and water on plants; the role of lepidopterans in pollination; and many other basic concepts. An additional benefit of the plant experiments is that you would be providing foodplants for the larvae or the ovipositing females and flowering plants for the adult lepidopterans.
Working with live, vibrant organisms, which react and change structurally, always produces a lasting impression as well as an informative, positive experience.
Ehrlich, Paul R. 1961. How to Know the Butterflies. Wm. C. Brown Company Publishers, Dubuque, IA.
Ferguson, Douglas C. 1972. The Moths of North America (Fasicle 20.2B Saturniidae). E.W. Classey Limited and R.B.D. Publications Inc., London.
Tyler, Hamilton A. 1975. The Swallowtail Butterflies of North America. Naturegraph Publishers, Inc., Healdsburg, CA.
Villiard, Paul. 1969. Moths and How to Rear Them. Funk and Wagnalls, New York.
L 919A Spicebush Swallowtail (P. troilus) Pupa . . $3.70; 3 . . $9.45 L 919B Tiger Swallowtail (P. glavcus) Pupa . . $3.70; 3 . . $9.45Now your students can study the life cycle of the painted lady butterfly (Vanessa cardui). The entire life cycle takes about 30 days. After hatching from a small, pale green egg, the painted lady larva pulls the edges of a leaf together and begins feeding within. After several molts (usually five), the larva hangs upside down and prepares to pupate. At this time the quiescent larva (known as the prepupa) is developing into a chrysalis (pupa).
After 24 hours, your students can watch as the caterpillar's skin splits and the chrysalis, which has formed under the skin, wiggles free. Within about four hours the chrysalis hardens and the adult emerges in 7 to 10 days. After emergence, the adult expands its wings and allows them to harden for a couple of hours before flying.
From five to seven days after emergence, female butterflies should begin to deposit eggs on the host plants. The small, pale green eggs, each with 12 to 14 longitudinal ridges, hatch after three to five days.
L 914 Kit . . . . . . . . . . . . . . $74.69 L 916 Refill . . . . . . . . . . . . $52.25 L 916B Replacement Egg-laying Disc . . $2.05
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L 907A Eggs (30-50) . . . $8.75
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per 25 . . $45.75
per 50 . . $89.95
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per 50 . . $50.60
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