Care Guide: Hornworms

Eggs

Your hornworm eggs will arrive in a small, plastic vial. It is best to hatch eggs on an artificial diet. You can easily construct a hatching chamber for 30 to 50 eggs using a plastic cup with a lid. Either pour liquid diet into the bottom of the cup or use a spoon to add a layer of solid diet to the bottom of the cup. Pack down the solid diet until it creates a good seal in the bottom of the cup. Whether liquid or solid, the layer of food should be no deeper than 7 to 10 mm (about ¼ to ⅜") deep. Allow liquid diet to solidify in the cup before continuing.

Place plastic netting in the cup with one end extended into the food. The netting helps support the food when the cup is inverted and allows a surface for the larvae to climb to reach the food.

Use a paper hole punch or other instrument to punch 4 holes through the lid. Invert the lid—inside facing up—on a table and line it with 2 sheets of tissue paper, filter paper, or paper towels. Put the eggs on the paper and reposition the cup (containing the solidified food and netting) over the lid. Gently work the lid back onto the chamber. Take care not to invert the cup so the eggs remain on the paper.

Place the hatching chamber, lid down, on a wire rack or use spacers (pennies) to elevate the lid slightly above a solid surface. This will allow air to circulate through the holes in the lid. Place the hatching chamber in a warm location at approximately 27° C (81° F) with a relative humidity of 40 to 50%. The eggs should hatch in about 3 days.

Eggs will also hatch on members of the Solanaceae (nightshade) family of plants. Suitable plants include tomato, eggplant, tobacco, and jimsonweed. Once hornworm larvae have fed on plants, few will accept an artificial diet. Larvae imprint on the first species of plant they feed upon and are voracious eaters. If you choose to hatch larvae on a suitable plant, you will need a plentiful supply of that plant before beginning your work. Place a leaf on a piece of damp filter paper in a petri dish and place the eggs on the leaf. Incubate as described above. Replace any material that becomes visibly moldy. Once the delicate larvae hatch and eat the leaf, use a small, clean brush to transfer them to additional leaves in petri dishes or directly onto plants.

It is easy to damage the young larvae by handling, so do not remove them from the hatching chamber until they are at least 2 cm long. Once the larvae have reached an appropriate size, remove them from the hatching chamber and into individual containers as described in the Larvae section.

Larvae

If you ordered hornworm larvae, they will arrive in a plastic cup with a small amount of media on the bottom of the cup. The larvae can live in their shipping container for several days, but it is best to move them to separate containers as soon as possible. Hornworm larvae grow quickly, and growth can be best observed when housed in individual containers. The larvae are 5 to 6 days old when you receive them and will complete their life cycle in 4 to 5 weeks.

It is easy to damage young larvae when handling, so do not remove them from the shipping cup until they are at least 2 cm long.

Remove the larvae from the shipping cup and put 1 larva into a housing vessel containing artificial diet. Carolina sells pre-poured vials containing diet in packs of 12 or packs of 50.

Do not put more than 1 larva into each vial. Lay the vials on their sides and place a lamp with a 100-W bulb (or equivalent energy-saving bulb) about 25 cm above them. Regulate the temperature by moving the lamp toward or away from vials. Check the temperature several times until it has stabilized around 27° C (81° F); thereafter, check it at least twice a day. Larvae must receive constant light to prevent their pupal stage lasting several months (diapause).

If you’re not using our Hornworm Nursery Kit or prefilled food vials, you’ll need to obtain some plastic containers with lids. An 8-ounce deli cup should be large enough to raise 1 hornworm larva. You will also need a supply of prepared diet. We sell a ready-to-use diet and a dry medium. Prepared diet should be stored in an airtight container in the refrigerator until use.

Pupae

Hornworm pupae are shipped in a roll of packing material. Gently unwrap the pupae and handle them carefully. Do not break the tongue cases, or the pupae will die. Place the pupae in a flight cage or other suitable container. Adult moths will emerge in 1 to 3 weeks.

To prepare mature hornworm larvae for pupation, remove each larva from its vial and wash any remaining culture medium from the vial with a jet of water. Do not use soap or detergent.

Hornworm larvae pupate underground. You can create a simulated, underground pupation chamber using the materials in your Hornworm Nursery Kit.

To simulate an underground environment, place a mature larva in a clean chamber and cover it with dry inert material (e.g., shredded paper, sawdust, potting soil) until the vial is about half full, then recap. Do not overfill or pack the vial; the larva needs space to pupate. Next, wrap each vial containing the larva and inert medium in newspaper and secure with rubber bands.

Place pupation chambers in an area where they will remain undisturbed. Do not remove the larvae from the vial until pupation has been completed. A pupa’s cuticle or exoskeleton is transparent at first, revealing its bright green inner tissues. During this time, the pupa is soft and can be easily damaged or killed. Gradually, the cuticle turns reddish-brown, then becomes opaque and hardens. The hardening process is known as sclerotization. The color of the pupa continues to deepen and darken to a dark brown or black as emergence approaches. Typically, mature larvae require 7 to 8 days to pupate. We advise that pupae be removed from their pupation chambers at days 10 through 12 to ensure that the cuticle has had sufficient time to harden and the pupae will not be damaged when they are examined or transferred. Place the pupae in a flight cage or other well-ventilated container. Adults should begin to emerge within 1 to 3 weeks.

Moths

To prepare for the moths to emerge, place fully formed pupae in a flight cage or other container. Maintain them at room temperature and expose them to a normal day/night cycle. The cage must have a vertical surface (cardboard, newspaper) that the moths can climb and cling to, or their wings will crumple as they unfold, and they will be unable to fly. Adult moths should emerge in 7 to 14 days.