How to identify a caterpillar

The transformation of a caterpillar to a butterfly or moth can be an exciting life cycle to learn about. Knowing the type of caterpillar and what it will change into is an important part of the experience. Caterpillars can be identified by visual examination, location and seasonal appearance. Caterpillars usually emerge from the eggs laid by spring butterflies and moths, later to continue the life cycle by transforming into a beautifully winged creature themselves.

Take a good look at your specimen and make sure that it is indeed a caterpillar. Worms are commonly mistaken as caterpillars and if you look closely, you can see the difference. When comparing the two, it is evident that a worm does not use legs to move, nor does it have a backbone. Caterpillars on the other hand, do use a leg-like mechanical system to get from place to place.

Note the colour and texture once you have determined it to be a true caterpillar. Most caterpillars have a unique colouring system that is exclusive to their genus. While some may have spots, others may not. Some will also have hairlike protrusions that cover their bodies.

Examine the plant where the caterpillar was found. All caterpillars have a food plant that they solely thrive on. For instance, the Monarch caterpillar will only eat the leaves of the milkweed plant, while the Black Swallowtail caterpillar exclusively munches on parsley and other members of the carrot family.

Write down on a notepad the characteristics of your caterpillar specimen. You may want to draw a quick diagram denoting its main characteristics and label each one for later recall. If you have a small container with air holes or a port-a-bug, you can temporarily take the caterpillar, along with a leaf from its food plant with you for continuous viewing. Just be sure to place it back on its food plant when you are finished and do not keep it in the container for any extended period of time.

Research the caterpillar using the characteristics that you have noted. There are many websites that have photos of each individual caterpillar species, along with the family information that it is connected to. If you have gathered enough information, such as its food source and appearance, an Internet search will aide in easy identification.


An activity that may be of interest to individuals with a desire to learn more about caterpillars is to create a habitat that will invite the different species to your backyard. By planting greenery particular to certain caterpillar families, you will be inviting them to live and breed near you. It is important to note that a caterpillar will lay its eggs on its food plant. The Monarch caterpillar will eat, lay eggs and form its chrysalis on the milkweed plant, making it possible to view its entire life cycle.


While it is encouraged to learn about caterpillars and their life cycle, it is still important to keep in mind that respect for their environment is also of great importance. Therefore, continuous disruptions, such as removing caterpillars from their food plants is not suggested.

Things You'll Need

  • Caterpillar specimen
  • Caterpillar’s food plant
  • Pen
  • Notepad
  • Vented container or port-a-bug
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About the Author

Jonae Fredericks started writing in 2007. She also has a background as a licensed cosmetologist and certified skin-care specialist. Jonae Fredericks is a certified paraeducator, presently working in the public education system.