Your Monarch Rearing Kit (available here) contains 14-16 first to third instar monarch larvae (caterpillars) that were started on an artificial diet.
Upon arrival, these larvae should be transferred to larger containers and provided with milkweed leaves. Monarch larvae will feed on all commonly available milkweed species (but do not confuse these with other plant species with a milky sap).
Milkweed plants can be collected in the field (cut stems) and stored in a refrigerator in plastic bags for 4-5 days. Leaves should be rinsed and dried before feeding. Do not feed the larvae leaves that are yellow, dried out, or moldy. If the milkweed plant has not been in your care, leaves should be washed in warm, soapy water, rinsed well, and dried before feeding. This will help prevent illness and death of the caterpillars due to pesticides. (Please note: Plants that have been sprayed repeatedly or sprayed heavily may contain residual pesticide that will harm the larvae, even with washing.)
To transfer the larvae, open the cups and use a fine paintbrush, toothpick or forceps to gently transfer the larvae to a suitable rearing container. Alternatively, you can add leaves to your rearing containers and place the open cups inside. The larvae will then crawl from the cups to the leaves.
Line the bottoms of the containers with paper towels. Add 2-3 leaves to each container and provide new leaves and a new paper towel every day or as needed.
Once the larvae have reached the last (5th) instar stage (approximately 1" in length), they will feed rapidly and can quickly run out of food. Watch the containers closely at this stage; you may have to feed the larvae twice a day.
Development times of larvae depend on the temperatures at which they are reared. At room temperature, the larvae should pupate 10-14 days after you receive them. Generally speaking, lower temperatures translate into longer development times and higher temperatures decrease development time.
To rear monarchs outdoors on living plants outdoors you will need to protect the larvae from numerous parasites and predators. Protection can be provided by using mesh “sleeves” with draw-strings on either end. The sleeve is placed over a plant, the larvae placed inside, and the drawstrings tied tightly. This method works well and little care is involved.