Has your child, or yourself brought a caterpillar home to store in a jar to watch the life cycle and now you're asking yourself,  “What do caterpillars eat?”  After all, you want it to survive long enough to see what type of beautiful butterfly it becomes.  Before you just throw any piece of plant in there, you should know that most caterpillars are fairly picky eaters.

Caterpillars are primarily herbivores but they will stray away from that rule if they cannot find enough food.  There are also some that will kill other caterpillars or butterflies so if you have two or more on your hands, they should not be kept together in the same jar.

These insects can be quite fussy when it comes to food.  Certain caterpillars have a specific choice of plant food that they need in order to complete their life cycle to stay alive.  If you remove a caterpillar from a plant, that needs to be the plant you keep in the jar with it.  Also, as the caterpillar grows, it will need more food so be sure you have access to this plant.  The bigger they get, the more they eat and caterpillars are always hungry.  Don't be concerned if you see old skin from time to time because they grow by molting.

If the plant food starts wilting you will need to give the caterpillar fresh food.  It cannot be stressed enough, the importance of feeding the caterpillar the right food.  For example, if you have a Monarch caterpillar, it will only eat milkweed plant leaves.  A Black Swallowtail will eat a few different things such as carrots, parsley, fennel and dill and a Queen Anne's Lace caterpillar loves caraway and celery.

Caterpillars will not only eat the leaves of the plant but sometimes the flower as well.  Host plants can often be perennials, shrubs, annuals and trees.  A Harvester caterpillar specifically only eats aphids so the butterfly always lays her eggs beside a colony of aphids.  It is important to try to determine what kind of caterpillar you have if you do not know what kind of plant it came from to be sure you choose the right food for it to keep it alive.  It is also interesting to note that caterpillars do not require water.  All of their water is obtained through their food.

The Easter Tiger Swallowtail, primarily found on the entire Eastern half of the United States feeds on a variety of broad leaf shrubs and trees, willow, lilac, tulip tree and birch while the Great Spangled Fritillary and Meadow Fritillary will eat only violets.  The Variegated Fritillary likes violets too but they also enjoy pansies, stone crops, plantains and passionflowers.  Additional caterpillars that feed on passionflowers are the Zebra Longwing and Gulf Fritillary, both species found primarily in Southern Regions.

A rare find is the Great Purple Hairstreak that turns into a beautiful butterfly with iridescent blue and gold markings.  It lives primarily on the West coast and eats only mistletoe.  So what do caterpillars eat?  Many varieties of plants, flowers, shrubs and trees but they are usually host specific.

Obtaining And Housing

Caterpillars can generally be found in the spring and early parts of summer if you search through bushes and plants.  When you find one on a plant, remove the whole stem and put it in the jar.  You shouldn't try to pick it up because they are fragile and some have urticating hairs and secretions that are skin irritants.

You can start out with a smaller jar but as they grow they will need to be transferred to a larger one.  You must be sure to cut a few holes in the top of the lid to allow for air but small enough so the caterpillar cannot escape.  You should also spray a very light mist of water in the jar once a day so it doesn't get dry but be sure to not over do it as they can drown from too much condensation.

You should know that after the caterpillar goes through the pupation stage and is about to emerge, you need to place a twig in the jar so that the butterfly can climb before they dry and expand their wings otherwise their wings could be deformed and they will be unable to fly.  When you release them, do so in a secluded area so they don not get eaten by a bird right away while the get familiar with their surroundings.