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    Insects - Animal Care

    Introduction to Life in the Classroom

    In several of the FOSS modules and courses, living organisms are brought into the classroom to be cared for and observed by K-5 students. Through the direct experience with organisms provided by these modules, we hope to engender in students a sense of respect for all life and to spark a desire to understand the complex systems that support life on Earth.

    This provides detailed information on how to obtain organisms, how to prepare for their arrival, how to care for them in the classroom, and how to instruct students to properly handle each animal. The animals in the modules were selected because they are abundant, safe for students, easy to care for, and hardy and well-adapted to classroom environments. Selected organisms that are nonexotic, commonly available from local and regional suppliers, and, in some cases, found in the natural environments in many regions. When investigations are carried out as described, the insects, worms, crustaceans, snails, and fish are not harmed in any way.

    Click on any animal to find out specific information about its care.

    Mealworms
    Milkweed Bugs
    Painted Lady Butterflies
    Crickets

     


    MEALWORMS

    200 Mealworms are scheduled to arrive at your school one week after the Insects Kit arrives. (Not including Holiday weeks or week before the holiday.) If you want them delivered at a different time, please contact the Kit Center.

    The mealworm is not a worm; it is a larva. Any similarity to a true worm is incidental. mealworm larvae are golden yellow and have 13 segments—a head, three thoracic segments, and nine abdominal segments Mealworm larvae are the counterpart of the familiar caterpillar in the butterfly story. They pull themselves around on six stubby legs, one pair on each thoracic segment.

    Mealworms are the larval stage of darkling (aka Tenebrio) beetles. Beetles, along with all their other insect kin (true bugs, flies, bees, wasps, ants, on and on), are members of the phylum Arthropoda, a word meaning jointed legs. Like all members of their phylum, insects wear their skeleton on the outside like a suit of armor. This is practical when they are under attack, but very inconvenient when they are trying to grow. Arthropods solved this problem by molting (shedding) this outer shell-like cuticle periodically. Immediately following the molt, the soft white larva expands before the new larger cuticle hardens. For mealworms this process repeats five times over a 2-month period, after which the larva is about 3 cm long. The final larval molt reveals the next stage, the pupa.

    Life cycle. Darkling beetles follow a life history known as complete metamorphosis. Like butterflies and moths, they go through four distinct stages during their life cycle. A female beetle lays eggs, as many as 500 in her brief lifetime of a month or two. The eggs are about the size of the period at the end of this sentence. After a couple of weeks the equally tiny larvae emerge from the eggs. The larvae are known as mealworms, but of course they are not true worms. The larvae are golden yellow and have 12 body segments. They are the counterpart of the familiar caterpillar in the butterfly story. Mealworms pull themselves around on six stubby legs that are all crowded at the front.

    The larvae seem to have two purposes in life: eat and grow. Beetles are arthropods, and like all members of their phylum they wear their skeleton on the outside like a suit of armor. This is very practical when they are being attacked, but very inconvenient when they are trying to grow. The arthropods have solved this problem by shedding (molting) their shell periodically. Immediately following the molt the soft, white larvae expand before the new larger shell hardens. This process may repeat half a dozen or more times over a 3-month period, after which time the larvae are about 2 cm (3/4") long. The final larval molt reveals the next stage, the pupa.

    The pupae don't eat and they don't move except for a twitch or two when disturbed. Inside, however, the mealworm is turning into a beetle, much the same as a caterpillar turns into a butterfly while sequestered inside the chrysalis. In 2 or 3 weeks the pupa splits open and out walks a beetle, white at first, but soon turning to brown and finally black after a day. The beetles mate and lay eggs, and the cycle repeats.

    Habitat and food. Mealworms and darkling beetles are rarely seen in the wild, but when they are, it is likely to be in a field where wild grasses flourish and seeds are plentiful. They are most often found in barns, grain storage facilities, and food preparation areas. This organism has benefited by living close to human enterprises, because we unwittingly provide a much better environment for the success of mealworms than could be found in the natural world. For this reason mealworms have become a minor pest in grain storage areas.

    Mealworms and darkling beetles are excellent classroom animals—they exhibit interesting behaviors, they are small but not tiny, they don't bite, smell, fly, or jump, and they are extremely easy to care for. Mealworms live right in a container of their food source: bran, cornmeal, rolled oats, breakfast flakes, or chick starter mash. All are excellent foods, but bran and chick starter are recommended. The food must be kept dry. Mealworms can go through their complete life cycle without any added water (they are very efficient at extracting water from the food), but it is recommended that small bits of apple, potato, or carrot be added from time to time.

    Mealworms should be kept in large, relatively flat containers. They seem to thrive best when the colony has a large surface area. Keep the bran about 2 or 3 cm (±1") deep in a basin, bus tray, aquarium, or plastic shoe box. If the container sides are steep and smooth, it is not necessary to keep the container covered. Adults and larvae seem to prefer hiding under bits of paper or light cardboard; the pupae give no indication that they care.

    The mealworm's preferred environment is very dry, moderately warm, and dark. A bit of apple provides extra moisture for the mealworms and seems to stimulate rapid growth. As the temperature increases, so does the rate at which mealworms advance through their life cycle. Under ideal conditions, in a classroom, the complete life cycle can take place in as little as 3 months, but more likely it will take 4 months. Cold slows the process almost to the point of suspended animation. Mealworms can be put into the refrigerator (not the freezer) for periods of time to stop metamorphosis.

    Food and Water. The mealworm culture must be kept dry. Mealworms can go through their complete life cycle without any added water (they are very efficient at extracting water from their food), but it is recommended that moisture continually be provided in the form of small bits of apple, sweet potato, or carrot. Otherwise the larvae and adults may attack each other in search of additional moisture. If carrot or sweet potato is used as the moisture source, the frass will be orange, adding evidence that the granules are waste rather than eggs.

    Mealworm Homes. Large cultures of mealworms (200 or more) should be kept in large, relatively flat containers. They seem to thrive best when the colony has a large surface area. Keep the bran 5–10 cm (2–4") deep in the clear plastic basin provided in the kit. If you want to expand your mealworm activities, any basin, bus tray, or old aquarium will do. If the container sides are steep and smooth, it is not necessary to cover the container.

    The mealworms's preferred environment is very dry, moderately warm, and dark. As the temperature increases, so does the rate at which mealworms advance through their life cycle. Under ideal conditions the complete life cycle can take place in as little as 3 months, but more likely it will take 4. However, students should be able to see their mealworms advance through the three important stages of larva, pupa, and adult in 4 to 6 weeks if the larvae are large and well advanced at the time they are introduced.

    Mealworms and darkling beetles are rarely seen in the wild, but when they are, it is likely to be in a field where wild grasses flourish and seeds are plentiful. They are most often found in barns, grain storage facilities, and food preparation areas. This organism has benefited by living close to humans, because we unwittingly provide a much better environment for them than can be found in the natural world.

    What to do when they arrive. Mealworm beetles are shipped in a container with a "breathing" cap to provide air. They need no special care but should be used as soon as possible, as they have a rather short life span. Keep beetles at normal room temperatures in low light. Store in a cool place at 45 to 65 F out of direct sunlight. At warmer room temperatures, larvae will soon pupate. Cover loosely with a paper towel to provide crawling space. Add slices of potato or carrot for moisture and add a substrate of bran for food. Replace as necessary or if it becomes moldy.

     

    Mealworm Life Cycle
    Stage
    How long?
    Food
    Moisture
    Other information
    Egg 7–14 days      
    Larva 30–90 days Bran Apple 5 molts occur
    Pupa 10–20 days      
    Adult 5–10 days Bran Apple Death: 30 days
    Egg The cycle continues.

     

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    MILKWEED BUGS

    75 Milkweed Bug Eggs are scheduled to arrive at your school one week after the Insects Kit arrives. (Not including Holiday weeks or week before the holiday.) If you want them delivered at a different time, please contact the Kit Center.

    Milkweed bugs are true bugs; beetles, moths, flies, and butterflies are not. Bugs have the usual complement of structures that they share with just about all other insects: six legs, three body parts (head, thorax, and abdomen), and two antennae. True bugs (order Hemiptera) do not have mouths for biting and chewing food—they have a tubelike beak for sucking fluids. The milkweed bug in nature sucks nutrients from milkweed seeds, but those in the classroom have been bred to feed exclusively on sunflower seeds.

    Another characteristic of bugs generally and milkweed bugs specifically is the stages they go through from hatching to maturity. Bugs go through simple metamorphosis. The insect emerges from an egg looking like a tiny version of the adult, with slight differences in body proportions and incompletely developed wings. The immature bugs are called nymphs. Newly hatched nymphs are analogous to the larvae of insects that go through complete metamorphosis, in that their prime directive is to eat and grow. As with all insects, in order to grow the nymphs must molt periodically. Just after molting the bug is creamy yellow with bright red legs and antennae. Within a few hours the body turns dark orange, and the legs and antennae resume their usual black color. The crispy little molts can be seen in the milkweed bug habitat about a week after the bugs hatch. Students may think their milkweed bugs are dying or that spiders and ants have invaded the habitat. It may take a while for students to figure out what the molts really are.

    Life cycle. Milkweed bugs advance through five nymphal stages (instars) as they mature. Each molt produces a larger nymph that is more completely developed. As the bugs grow, the dark wings appear on the backs of the bugs as black spots. Other black markings start to appear and eventually develop into the characteristic patterns of black and orange by which the adults of the two sexes can be identified. The last molt reveals the adult. There is no pupal resting stage as in insects that undergo complete metamorphosis—the large nymph simply molts, and away walks the adult.

    Milkweed bugs continue to feed as adults, inserting their long beaks into sunflower seeds to suck out oils and other nutrients. Mating is easily observed, as the two mating bugs remain attached end to end for an extended time. It is possible to distinguish female and male adults by body markings. Look on the ventral (belly) side of the bugs. The tip of the abdomen is black, followed by a solid orange segment (with tiny black dots at the edges). If the next two segments following the orange band have solid black bands, the bug is a male. However, if the segment following the orange band is orange in the middle, making it look like it has two large black spots on the sides, followed by a segment with a solid black band, the bug is female. (See the Milkweed Bug Male and Female poster.) Males tend to be smaller than females. Look for mating bugs to identify males and females—there will always be one of each in such pairings.

    Several days to 2 weeks after mating, the female lays a cluster of 50 or more yellow eggs (which turn orange fairly quickly) in a wad of cotton. The eggs can be removed to a new culture container or left in the habitat to continue the life cycle.

    Milkweed bug habitat. Culturing milkweed bugs is fairly easy. The bugs require no soil or green plant material. Just about any container is suitable for a habitat. Because milkweed bugs can walk on any surface, including smooth plastic, glass, metal, wet surfaces, and all textured surfaces, the habitat must be closed tightly, and the ventilation holes must be tiny so the first instar nymphs can't escape.

    We suggest a plastic zip bag for the habitat container. Use a pin to poke a hundred holes in the bag, and install a water container in the bottom. To add interest, put a branch in the bag and attach a bundle of raw, shelled sunflower seeds and a cotton ball to the branch. Hang the bag from a paper clip next to a wall out of direct sunlight.

    Maintenance. Maintenance is minimal. Keep an eye on the water level, and when it gets low after 3–4 weeks, add water and perhaps replace the wick. A new bundle of 20 to 30 sunflower seeds each month should be adequate for a modest culture of 25 bugs. The culture may start to look a little messy after a month as little brown spots of waste appear on the walls of the bag and the molts start to accumulate. Transfer the branch, water fountain, and bugs to a new bag to renew the aesthetic appeal of the culture.

    What to do when they arrive.

    • Eggs are shipped on a wad of floss. If you are unable to begin the investigation when the eggs arrive, they may be kept in the container at cool room temperatures or refrigerated for short periods; otherwise they will hatch within one week. If the eggs have hatched upon arrival, add a few sunflower seeds and hatched nymphs to the vials for distribution to the students.
    • Keep adult males and females in separate containers. A 1/2-liter container with small air holes can be used for a few days. Add a few sunflower seeds and a moist paper towel wick for moisture. To keep adult milkweed bugs for a longer period of time, place in milkweed bug habitats with sunflower seed packets, water fountain, twigs, and floss for eggs.

    End the life cycle. As long as the four needs are attended to, new generations of milkweed bugs will continue to flourish in the habitat. At some point you may want to end the cycle. Although the bugs would probably soon perish if released into the environment, it is not suggested that you do so, as they were not originally from the environment. Place the bag in the freezer overnight to kill the bugs; discard the bag in the trash.

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    PAINTED LADY BUTTERFLIES

    5 Painted Lady Butterfly Larvae are scheduled to arrive at your school three weeks after the Insects Kit arrives. (Not including Holiday weeks or week before the holiday.) If you want them delivered at a different time, please contact the Kit Center. They arrive in a plastic container with a centimeter or two of green goop that looks like guacamole. The ventilated lid holds a piece of filter paper over the top of the container. Keep the lid and paper on the container at all times. The painted ladies will spend all of their larval days, perhaps 2 weeks or a little more, in the container eating the food layer, molting, and growing to a length of 4 cm (1-1/2") or a little more. They require no special attention other than to keep them in a well-lighted area, but out of direct sun and safe from temperature extremes. After the larvae are about 2 cm (3/4") long, it is all right for students to remove the larvae from the containers from time to time for close observation of structures and behaviors.

    Life cycle. In due course the larva receives a biological message to climb to the top of the container, spin a little knob of silk onto the filter paper, and attach its rear end firmly to the knob. The larva hangs head down and assumes a characteristic J shape, indicating that pupation is only a few hours away. If you are vigilant, you might be able to observe the final molt as the fuzzy outer skin splits near the head to reveal the smooth, curiously molded, slightly iridescent pupa ensconced in its chrysalis. As the pupa writhes around, the skin is pushed up and off the body until it is a crunchy little nub pressed up against the paper. The painted lady lapses into a period of relative quietude, hanging motionless except for brief fits of wriggling, especially when disturbed. At this time the pupae attached to the paper should be moved to a larger cage.

    For a week or 10 days the pupa undergoes dramatic physical and biochemical transformations. The chrysalis gradually darkens until it is dark gray-brown, and the orange color of the wings starts to show through. This is when you can expect the adult to emerge, which happens quickly. The chrysalis shell splits near the bottom (head end), and the butterfly reaches out with its legs and grasps the outside of the chrysalis. The head comes out, and then the abdomen and wings are pulled free of the chrysalis shell. The emergence takes a minute or less.

    The fresh new butterfly clings to the chrysalis shell with its soft, crumpled wings hanging down. Over the next hour or two the abdomen pulses as it pumps fluid into the veins of the wings, expanding them to their fully extended shape. During this time the butterfly ejects a splat of red liquid. Students may be alarmed, thinking it is blood, but it is a waste fluid that the butterfly unloads as it prepares for its new life. In 3 or 4 hours the butterfly takes wing as a flying insect.

    Maintenance. Painted lady butterflies don't require much as adults. They will drink dilute sugar solution and fly around looking for mates. Place the cage where sunshine will fall on it for a few hours each day. If mallow, a common weed in many parts of the country, is available, you can place a small bouquet of leaves in a vial of water. After the butterflies mate, they will lay eggs on the mallow leaves. If you want to raise a second generation of painted lady butterflies, provide mallow leaves for the larvae to eat.

    After a month the adults will die, not because of any ill effects caused by captivity, but because that is their normal life span. Even though it is never advisable to release study organisms into the environment, if a painted lady butterfly "escapes," it will not be an environmental disaster—painted ladies are already well established throughout the country.

    What to do when they arrive. Butterfly larvae are shipped with their own food in the shipping container. Warmer temperatures will encourage larvae to grow more quickly. Maintain container out of direct sunlight. No further care is necessary, as they will pupate within 7 to 10 days. (See above)

    Prepare a feeding station. A butterfly feeding station can be made from a standard insect water fountain. Use a hole punch to make a hole in the center of the cap of a vial. Roll up an 8-cm (3") square of paper towel and push it through the hole in the cap. Push the vial into the plastic vial holder to prevent the fountain from tipping over.

    Butterflies feed by sipping nectar through their long coiled proboscis. A substitute nectar can be made with sugar and water. Put 1/4 teaspoon of sugar in a vial and fill it with water. Attach the wick cap to the vial. Cut a crude flower from a piece of red or orange paper, make several criss-cross cuts in the center, and push the vial through. The flower will attract the butterflies and give them a place to land.

    Provide mallow leaves (optional). When adults emerge, provide a bouquet of fresh mallow leaves in the cage. Use the hole punch to punch a few holes in a plastic cup lid. Fill the cup with water and snap on the lid. Stick leaves and small branches of mallow through the holes. Females will lay eggs on the mallow leaves.

    Watch for egg hatching. The eggs hatch in a week or so, and it is possible to start the whole process over again. Larvae will thrive if you transfer them to fresh mallow leaves. They must be kept in a covered container because they are very mobile. A supply of mallow leaves can be kept in the refrigerator. If you do not want to let the eggs hatch, put them in the freezer for a few days to end the life cycle. Eggs, larva and adults should not be released into the wild as it can disrupt the local ecosystem.

    Discuss death. Butterflies don't live long. After 3 weeks they will be tattered and tired. With luck they will have fulfilled their destiny by producing eggs. Discuss the inevitability of the death of the butterflies and that it is not caused by captivity or the result of any failing on the part of the caregivers. Butterflies just don't live very long.

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    CRICKETS

    12 crickets are scheduled to arrive at your school three weeks after the Insects Kit arrives. (Not including Holiday weeks or week before the holiday.) If you want them delivered at a different time, please contact the Kit Center.

    Background. Many people recognize crickets without even seeing them. They identify the familiar chirping sound made by the male cricket in his efforts to attract a mate. The sound is most often heard at night when crickets are most active, prowling about looking for food, moisture, and a consort.

    Crickets undergo simple, or incomplete, metamorphosis; they molt several times as they grow, each molt revealing larger, more fully developed crickets, until the last molt results in adults.

    The female cricket has a structure protruding from the rear of her abdomen that students often think is a long stinger. It is an ovipositor, which the female thrusts into moist earth in order to lay her eggs well below the surface. When the eggs hatch, the nymphs dig to the surface, where they fend for themselves.

    Crickets have other interesting features, starting with a pair of spikes that extend out from the end of the abdomen in both sexes. The cricket has two pairs of wings, the front two of which are equipped with rasp-like adaptations that, when scraped together, produce the chirp. The hindmost pair of legs are greatly enlarged, allowing the cricket to spring huge distances when motivated by alarm or other stimuli. On the front-most pair of legs are membranes that are sensitive to sound vibrations, so in effect the cricket has its ears on its legs. The antennae are long, lithe, and sensitive. It is fascinating to see the exquisite control the cricket has over these wispy structures as it probes and feels its environment before rushing in.

    The cricket most used for classroom cultures is the house cricket. It lives in containers quite well and is content to eat seeds, fruit, grass, and dry dog food. However, crickets are good at escaping confinement. They will gnaw through paper or cardboard quite quickly, and if they are overcrowded, hungry, or thirsty, they will chew through nylon mesh covering a cricket container. For this reason it is necessary to cover the container with metal screen.

    Cricket habitat. The FOSS cricket habitat has three chambers. One contains soil that is kept moist. This is where the females will lay eggs. A second chamber contains dry sand. Food should be placed in this area so that it will not mold. The central area is the exercise yard with structures for climbing and hiding.

    Crickets need paper, sand, or soil to get around because their feet are not adapted for holding onto smooth surfaces. A large or complex cricket culture container will allow the crickets to display preference for variables such as moisture, temperature, and structure. Crickets prefer a hot, dry environment. If they are kept in a humid environment, they can develop a fungus, so lots of ventilation is needed. They can go into a moist environment to eat or lay eggs, but they must be able to retreat to dry ground. If you like, you can train a lamp on the central part of the habitat, the crickets will congregate there to bask. And you will probably get a song tossed in as part of the bargain.

    What to do when they arrive. Crickets are shipped in a container with crumpled paper. They dislike overcrowding and should be transferred to a terrarium as soon as possible. To remove the crickets from the box, slit the tape. Enclose the box in a plastic bag and shake the crickets into the bag. Then transfer the bag of crickets into the cricket habitat you have made. This will be easier than shaking them directly from a box into the habitat. Crickets may be fed oatmeal, bird seed, small pieces of fruit or lettuce, or dried dog food. Prepare the water fountain provided in the kit. Crickets can also be purchased at pet stores or at stores that sell reptiles and amphibians.

    What to do with the crickets when the investigation is completed. You can keep the crickets in a terrarium with a screened lid. Follow the care you've been providing and they should be fine. Crickets have a short lifespan so a long-term colony may not be possible. Offer the crickets to another classroom that will be conducting the investigation. They are also a good food source for reptiles and amphibians. Crickets should never be released into the wild as they may disrupt the environment and interfere with local organisms.

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