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Rearing How-To’s for Activity 3

There are many different methods that can be used to rear monarchs - pick and choose what works best for you, but keep in mind some of the best practices provided below. As a part of their online training video series, the Monarch Larva Monitoring project produced a video about rearing monarchs and reporting data to the project. The Monarch Joint Venture has also produced a handy monarch rearing flyer! You can also visit our Rearing and FAQs page for more information.

Best Practices for Rearing Monarchs Safely

Rearing Container
  • Keep eggs and larvae in individual containers (1 monarch per container) lined with a moist (but not dripping wet) paper towel to keep the milkweed from drying out. This helps prevent the spread of diseases or the parasite, OE. A petri dish or other small clear glass or plastic container works well for this. The container should be able to withstand washing and soaking in a bleach solution. Label the container with the date of collection, stage of monarch (egg, 1st instar, 2nd instar, etc) and location of collection.
  • Keep containers out of direct sunlight or hot places. High heat will kill the monarch inside. Exposing the containers to natural daylight and temperature changes will allow monarchs to receive natural cues needed to trigger migration.
  • Rear larvae (caterpillars) in large jars, deli tubs, or other relatively large clear containers. The containers should be easy to open (since you need to clean them every day), have screen coverings or holes for air flow, and allow you to see the larva inside. They should be large enough for the adult to expand its wings when it emerges. 5th instar monarch larvae preparing to pupate will do so from the lid of the container.
  • Be sure to transfer the label with larvae if you need to move them to larger containers. This label contains the information you will need to report your data for Activity 3.
  • Wash your containers in between use among caterpillars. If you have used your container for monarchs before, wash it well and then sterilize it with a weak (20%) bleach solution before using it again.
  • Containers must be cleaned and larvae provided with fresh milkweed DAILY. Do not leave your monarchs unattended over the weekend. Milkweed can be found in many places - alley ways, roadsides, in parks and gardens. You can pick several days' worth and keep it in a plastic bag in a refrigerator. Wash it with water before feeding to larvae. Milkweed stays fresher if you keep the end or leaves moist by wrapping it in a wet paper towel and covering the towel with aluminum foil, or use florist water tubes. A moist paper towel in the bottom of the container also helps keep the leaves from drying out.
  • Do not handle monarchs while they are molting, pupating, or eclosing. Monarchs remain in the larval stage for about 2 weeks after hatching from eggs. During this time, they go through five instars, which means that they molt (shed their skin) five times. While they are molting, they often crawl up the side of their container or onto the lid, and remain this way for 12-24 hours. If you look closely, you will notice when their old head covering is about to come off. You may be able to find this covering in your container. They will eat the rest of their skin!
  • Dispose of any dead larvae from containers and record on your Activity 3 datasheet. Some mortality during during the larval stage is not abnormal. Mortality can be caused by a viruses or bacterial infections, parasites, or by contaminated milkweed. You should not feel bad about this if you have been feeding your larvae regularly and keeping their container clean. It happens and there's nothing to prevent bacterial or viral infections.
  • Do not handle butterflies for the first 4 or 5 hours after they eclose. Keep them in their containers until the next day and then release. Hold the butterflies carefully with their wings closed when you release them, or simply open their container to let them fly free. Don't forget to note the day of emergence from the pupa and the sex of the adult before you release it. Record this information on your datasheet and report it under your account for MLMP.