Corn earworm (Helicoverpa zea)

Corn earworms (also called tomato fruit worms and tobacco budworms) are catepillars of the moth Helicoverpa zea. These caterpillars are considered to be a pest species on plants such as corn, soybean, tomato and tobacco, and are easily reared from egg to adult in about three weeks.

Availability: You will be able to follow your lepidopteran through egg, six larval instars, pupal and adult stages over the course of 3-4 weeks. To do so, we will provide you with eggs. Unfortunately, eggs are available only periodically from our colonies about once a month.

After you have a cage (a small screw-top jar works fine) and supplies (food) ready, contact Liz ( to schedule a pickup time (right after class is convenient). We will provide you a piece of cheesecloth covered with a dozen or so eggs and enough artificial diet for the neonates (newly hatched larvae) to live off for a few days. Neonates are tiny when they hatch (about the size of a period) and will starve to death within a few hours if not transferred to diet. To avoid this, we suggest that you keep the eggs in the transfer container and allow the larvae to feed on the artificial diet for a day or two.

Housing: These caterpillars can be easily reared through adult emergence in a small plastic or glass container. Use a container that you can make observations through. The main challenge is to retain enough moisture, but to avoid allowing the early instars to escape or suffocating later instars. The best containers are ones with a loosely-fitted lid or screw top. Keep the lid tight for the first few instars. When the larva has completed three molts, either loosen the lid or poke a few tiny holes in the lid. Periodically remove frass to avoid disease. The earworms can remain in this container during the larval stages.  When your insect pupates, transfer it to the adult container.

Adults require more space to move about and fly than the larvae. Minimally, an adult requires a container that is about a pint size or larger. We use plastic ice cream buckets sealed with a cheesecloth lid. Common containers that have worked in the past include medium size jars, yogurt containers, and juice containers. Be sure to clean your container first! If you do not have a lid, you can use a piece of cloth or paper towel and a large rubber band to keep the moth in the container. We will also set you up with a small vial to provide an artificial nectar source for the adults, as well as instructions.

Food: Part of the challenge of raising herbivores is providing them with fresh, healthy food. This species can be reared on the artificial diet provided for a few days. However, you should try to rear your caterpillars on plant material. Corn earworms develop best on fresh plant material, such as corn, tomatoes, or soybeans, and they prefer to feed on the fruit (tomatoes, corn kernals, beans).

Some important guidelines:
Use only fresh organic vegetables when feeding your caterpillars. Non-organic vegetables often contain traces of insecticides which may be specifically directed against your caterpillar (these are pest species)!  Replace food daily to avoid disease and microbial spoiling. Use small, whole portions. Keep the unused vegetable portions in the refridgerator to limit spoiling.  For your own ease, try to use food that will not spoil rapidly. 

Pupae do not need to eat food. Adults require nectar or a sugar water source to survive. Adults can be fed on a 10% honey water solution (1 part honey dissolved in 9 parts water) in a glass vial stuffed with a cotton plug (talk to us - we will provide this in the start-up kit). The honey water and cotton plug should be changed daily to avoid microbial contamination.