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Rearing Butterfly Caterpillars

Chrysalis and Pupation
Parasitiods and Predators

When your caterpillars emerge from eggs or your caterpillar shipment arrives, check it immediately! DO NOT, I repeat, DO NOT move your caterpillars if they are not moving their back legs (prolegs) on their own. Caterpillars molt, or crawl out of their skin, about four times before becoming a chrysalis. The time period between molting is called an 'instar'. Monarch caterpillars go through five instars before pupating into a chrysalis. If you move your caterpillars while they preparing to molt or in the process of molting, they could (but not necessarily will) die. Their skin never grows. As they grow, they must leave their old smaller skin. To prepare for molting, they will suddenly stop eating and sit for a while in one spot. They are preparing to molt. They will lay a silk pad and lock thier backlegs (prolegs) into the silk mat. After about a day, they will split their skin at the head and simply slowly crawl out of thier old skin. In most cases, they will then turn around and eat their old skin.

When caterpillars prepare to molt, they draw thier heads out of their head capsules. When they start to molt, their head capsule pops off. Only when caterpillars pupate will their head capsules says attached to their old skins. In the photographs below, notice the size difference between the old head capsule and the new head capsule.

Photographs of molting caterpillars are below.

It is best to place the container in which your caterpillars arrive into the rearing container you have prepared. If you must move the caterpillars, tickle their rear ends. If they move their back legs, it is safe to gently pick them up and move them. Remember, stay sterile. Wash your hands throughly before touching your rearing cage or caterpillars!

Be sure to feed them enough to prevent them from running out of food. Cannabalism is not uncommon when they are hungry. Their cut food needs to be dry yet fresh, not wet with water on the surface of the leaves. If their cut food dries out quickly, make a 'vase' for it. Wrap the cut stem of their food in wet paper towels and wrap the paper towels in foil. Presto! This keeps the cut stems fresh and is easy to clean. Simply toss in the trash. A container of water often results in caterpillars floating in the water. Water pics, used by florists are also a great method to keep stems fresh. If you use water pics, be sure to sterilize them between containers of caterpillars.

The size of the adult butterfly depends greatly upon the amount of food the caterpillar eats. If the caterpillar runs out of food often, the chrysalis and the resulting adult butterfly will be smaller than it could have been.

If mold starts to grow in their container, be sure to clean it carefully. Wet food, overcrowing, running out of food, temperature fluctuations of 15 degrees or so, and other stress factors can and usually will cause your caterpillars to succumb to disease. At the bottom of this page are photos of diseased caterpillars and other signs of trouble you may run into with your rearing. Don't dismay! Remember, these diseases come from the wild and are common in nature. Some of these diseases are purchased by farmers and gardeners for use in home gardens, crops, or forests. If your caterpillars become diseased, it doesn't mean you did something wrong. Be as careful as possible yet please do realize that disease is normal in nature.

Caterpillar droppings are called frass. When caterpillars run out of food, they will often eat frass. It is important to keep enough fresh food in thier container and to keep it clean and dry.

A Monarch caterpillar 1/4 inch long has molted.
Notice the head capsule lying next to its head.
Available as photograph
A closeup of the head capsule after molting.
Available as photograph
Spicebush Swallowtail
A molting Spicebush has crawled half-way out of its skin.
Available as photograph
Spicebush Swallowtail
A Spicebush has molted completely.
It has crawled totally out of its outer skin.
Available as photograph
A Monarch caterpillar lits its legs out of its skin as it finishes molting.
Available as photograph
Sleepy Orange
A Sleepy Orange caterpillar has finished molting.
It's empty skin is white.
Available as photograph
Gulf Fritillary
A Gulf Fritillary eats it's old skin after molting.
Available as photograph