Larvae used in: Insects
Waxworm – Galleria mellonella
Background. The waxworm is the larva of the greater wax moth, a small nondescript flying insect that lays its eggs in beehives, where the growing larvae feed on honey and wax. A robust hive of honey bees can repel the onslaught of waxworms, keeping the damage to a minimum, but waxworms can overrun and destroy a stressed colony.
Waxworms are white to tan, plump, clearly segmented, and moderately active. They are a little softer than mealworms, so they must be treated somewhat more gently, but they are still very easy for first and second graders to handle. The waxworm has 13 segments (head, three thoracic, nine abdominal) and the mandatory six legs. But unlike the mealworm (a beetle), the waxworm has four pairs of leglike structures called prolegs—one pair on abdominal segments three through six. These prolegs are equipped with muscular pads called claspers, which help the larvae hold onto surfaces, and the 13th segment (tail) also has a clasper. The waxworm has bristles (stiff hairs) on its body and a row of clearly visible openings called spiracles along each side. The larvae have no lungs—oxygen enters through these spiracles and is distributed through the fluids of the body.
Waxworms, like all moths, make silk. Silk is used as a lifeline, as a webbing over which the larvae can walk, and as a material to build a protective cocoon. The silk is produced in a gland under the head and extruded through structures called spinnerets.
Waxworm habitat. Like mealworms, waxworms apply themselves to a career of eating and growing. The medium in which they live in the classroom is also their food—honey or sugar and glycerin mixed with baby food and a trace of vitamins. Any large jar containing 7–10 cm (3–4") of food will culture 100 or more larvae. They prefer to be kept in the dark, but this is not essential. Small numbers of waxworm larvae can be kept on desks in covered cups with a little food for students' close and continual observation.
You can expect some of the waxworms to die, both in the student cups and in the class culture. A dead larva is recognized by its conspicuous inactivity and a change of color from creamy white to tan to gray to black. Dead larvae should be thrown away. A pair of forceps is included in the kit for such operations. If a deceased larva is removed from a student cup, replace it with a healthy one from the class culture. Waxworm lifecycle. The waxworm will advance through the major stages of its life cycle in as little as 6 weeks if the temperature is 28–34°C (82–93°F), more slowly at room temperature. After gorging itself as a chubby white larva, the waxworm is prepared to pupate. In the dark it climbs to the top of its container and spins a cocoon on the wall; in the light the larva spins a cocoon in the medium. Inside the cocoon the larvae rest and transform into pupae. After a week or two the adult moths emerge. The adults neither eat nor drink. After mating, the females lay eggs in the culture and die. If you want to collect the tiny eggs, fold a piece of waxed paper in tight little accordion folds, like a fan, and put it in the container with the adult moths. If the eggs collected in this way are transferred to a container with fresh culture medium, they will hatch after about 10 days, and the cycle will repeat.
Obtaining waxworms. Waxworms can be obtained from bait stores, pet stores that cater to bird and reptile fanciers, or biological supply houses. The ones from biological supply houses are more suitable, and they arrive in a supply of food medium. Get 75–100 of the largest ones available. What to do when they arrive. Larvae are shipped in a container with food. If storage is necessary, they may be held in their shipping containers at 35 to 40ºF for a short time. At warmer room temperatures, larvae will pupate in as little as six weeks.
If the waxworms arrive in a nutritional medium, move them to the large plastic jar, medium and all. Screw on the ventilated lid.
If the waxworms are in a neutral medium like sawdust, remove them from the sawdust and put them in the large jar with one cup of homemade medium. Make a tube of dark paper to slip over the jar, or place it in a paper bag or box to keep it in the dark.
Providing warmth. Waxworms do best in temperatures above 28°C (82°F). If this is not the temperature in your classroom, provide a lamp or two for additional warmth. Create a hot spot in your room where the class culture and students' cups of waxworms can be stored in the dark. At normal classroom temperatures the waxworms may stay in the larval and pupal stages for an extended period of time. Pupae may make hard shells instead of cocoons. That's OK; the waxworms are still valuable for comparison with mealworms. Don't give up—even without the lamp trick the wax moths will eventually emerge. Preparing waxworm medium. This recipe makes enough waxworm medium for students to put into their cups and for the classroom culture.
4 oz. glycerin
1/4 cup sugar
1/4 cup hot water
1 box (8 oz.) baby cereal (oat)
Dissolve the glycerin and sugar in hot water. Cool the solution. Pour the whole box of cereal into a large bowl. Pour the solution in a very thin stream into the cereal while stirring enthusiastically—it should take about 2 minutes to dribble all of the liquid if you are pouring slowly enough. The medium will be somewhere between sticky, lumpy, and crumbly, and it will smell very pleasant. Store it in a plastic bag.
Waxmoth mating. When a significant number of adults have emerged, put them all in an empty 2-liter jar where they can mate and lay eggs. The moths are inactive early in the day, so plan to transfer them in the morning. Cover the jar with a ventilated lid. Have it sitting loosely on the jar during the transfer. Screw it on securely after transfer is complete. If you want students to continue watching the life cycle of waxworms, prepare a batch of medium to nurture the next generation. Follow the recipe above, or use any stored medium that you haven't used. Clean out the original class waxworm jar and make it ready for the next generation.
What to do with them when the investigations are completed. The humane way to end the cycle of waxworms is to put the culture in a freezer overnight and then dispose of them and the medium in the compost. Rinse the jar thoroughly. Waxworms should never be released into the wild as they can damage local organisms and the environment.