You may find gathering and rearing caterpillars to be a fascinating and rewarding experience. Finding, feeding and housing caterpillars - especially those of any endangered species - is a major contribution to enhance the ecosystem. Caring for caterpillars can help ensure they pupate and emerge as winged adults that lay eggs. You can find caterpillars by searching plants or bushes during spring and early summer. According to the University of Wisconsin Entomology Department, the entire life cycle from larvae to pupae for many species is just a couple weeks.
Familiarise yourself with caterpillar species and the plants they feed on in your area. Have a guidebook or printout from reputable website(s) with you before heading out for the hunt.
Search for caterpillars on warm, sunny days (21.1 degrees C plus) by looking for leaves with caterpillar dung (also called frass) on them and cut-out sections or holes in them. This is an obvious sign of happy, healthy prolific specimens to get your hands on.
Collect the caterpillars by lifting the entire stem they are feeding on rather than picking them up with your fingers off the stem or leaf. Not only are they quite delicate, but many are also poisonous with barbs or secretions that will irritate your skin.
Place the stems of the food plant and the caterpillar in a jar with holes in the lid for air. Be sure to collect or know you can cultivate enough host plants to feed the caterpillar throughout its short larval stage.
Order caterpillars through an insect supply house if you are short on time or if it is off season for caterpillar hunting. There are several reputable companies that supply caterpillars for a fee. Ensure that you can also obtain an ample supply of host plants that can be found in the growing season or purchased through a supply house.
If it is extremely warm with full sun, the caterpillars will most likely be found on the underside of the leaves. In this case, turn the leaves over. Do not take more than six or so caterpillars from a particular site, to be environmentally responsible. If you find a caterpillar on the ground then it is either searching for a food plant or looking for somewhere to pupate. Best to leave it alone unless you are absolutely sure of its food source. Place a block of oasis (a type of hard green sponge used for flower arranging) on the bottom of the jar soaked in water to support the stems of the food source.
There are numerous species of green caterpillars that all look similar. Unless you identify one of these caterpillars properly with an expert entomologist, it could starve to death because the proper food source could be misidentified.