Caterpillars have chewing mouth parts and feed on vegetation, generally leaves of a specific type of plant. Some caterpillars have such specific diets that they will only eat one kind of plant, while others may feed on a wide variety of plants. Some specialist caterpillars feed on animal dung, are predators on other insects, or are even aquatic, feeding on algae.
Caterpillars have chewing mouth parts and feed on vegetation, generally leaves of a specific type of plant. Some caterpillars have such specific diets that they will only eat one kind of plant, while others may feed on a wide variety of plants. Some specialist caterpillars feed on animal dung, are predators on other insects, or are even aquatic, feeding on algae.

© 1999, CHIN. All Rights Reserved.

Video of a caterpillar eating.

This caterpillar is munching on grass.

Insectarium de Montréal

CANADA
MEXICO
UNITED STATES
© Insectarium de Montréal


Caterpillars eat plants.

A caterpillar eating a plant.

E.T. Jones (PMA)

UNITED STATES
CANADA
MEXICO
© E.T. Jones (PMA)


Butterflies, like all insects, are members of the phylum Arthropoda which includes all animals that have jointed legs and an exoskeleton or external skeleton. It is the nature of this exoskeleton that makes it necessary for all arthropods to moult. The exoskeleton, which is made of a material called chitin, cannot grow and expand as the animal grows. For this reason it is regularly shed or moulted, and replaced with a larger exoskeleton to allow the animal to grow. It is important to remember that it is only the caterpillar that moults and the butterfly, which is the adult stage, does not moult.
Butterflies, like all insects, are members of the phylum Arthropoda which includes all animals that have jointed legs and an exoskeleton or external skeleton. It is the nature of this exoskeleton that makes it necessary for all arthropods to moult. The exoskeleton, which is made of a material called chitin, cannot grow and expand as the animal grows. For this reason it is regularly shed or moulted, and replaced with a larger exoskeleton to allow the animal to grow. It is important to remember that it is only the caterpillar that moults and the butterfly, which is the adult stage, does not moult.

© 1999, CHIN. All Rights Reserved.

Caterpillars moult into butterflies.

This caterpillar is moulting.

Insectarium de Montréal

MEXICO
UNITED STATES
CANADA
© Insectarium de Montréal


The word caterpillar refers to the larval stage of the butterflies and moths, so all caterpillars become either a butterfly or a moth. There are, however, some larval insects that look very similar to caterpillars. The most likely to be encountered are the larvae of sawflies, which are actually wasps and not flies. These larvae look so much like caterpillars that sometimes even the experts mistake them for caterpillars.
The word caterpillar refers to the larval stage of the butterflies and moths, so all caterpillars become either a butterfly or a moth. There are, however, some larval insects that look very similar to caterpillars. The most likely to be encountered are the larvae of sawflies, which are actually wasps and not flies. These larvae look so much like caterpillars that sometimes even the experts mistake them for caterpillars.

© 1999, CHIN. All Rights Reserved.

Identifying a butterfly to the species level by the characteristics of its caterpillar is difficult at best, for several reasons: first of all, colours of the caterpillar will change as it grows, getting darker just before moulting. Secondly, shape is not always a good trait because the caterpillar will look different depending on the instar.

It should also be noted that at present there aren’t any truly comprehensive guides. This is not to discourage the enthusiast because simple guides for identifying caterpillars at least to the family level exist, and rearing caterpillars to the adults is encouraged to help in better understanding early life stages. Generally speaking, adult stages are well understood, but larval stages need further investigation.
Identifying a butterfly to the species level by the characteristics of its caterpillar is difficult at best, for several reasons: first of all, colours of the caterpillar will change as it grows, getting darker just before moulting. Secondly, shape is not always a good trait because the caterpillar will look different depending on the instar.

It should also be noted that at present there aren’t any truly comprehensive guides. This is not to discourage the enthusiast because simple guides for identifying caterpillars at least to the family level exist, and rearing caterpillars to the adults is encouraged to help in better understanding early life stages. Generally speaking, adult stages are well understood, but larval stages need further investigation.

© 1999, CHIN. All Rights Reserved.

Some caterpillars, especially the caterpillars of the Arctiid moths such as the woolly bears, do have hairs that can cause a burning sensation. Not everybody reacts to these hairs however. In tropical countries some of the hairy caterpillars are known to cause a very severe reaction and it is generally best to avoid touching any hairy or spiny caterpillars in these areas.
Some caterpillars, especially the caterpillars of the Arctiid moths such as the woolly bears, do have hairs that can cause a burning sensation. Not everybody reacts to these hairs however. In tropical countries some of the hairy caterpillars are known to cause a very severe reaction and it is generally best to avoid touching any hairy or spiny caterpillars in these areas.

© 1999, CHIN. All Rights Reserved.

Some tropical caterpillars have poisonous spines.

Some tropical caterpillars have poisonous spines.

Insectarium de Montréal

CANADA
UNITED STATES
MEXICO
© Insectarium de Montréal


Some caterpillars have poisonous hairs.

Some caterpillars have poisonous hairs.

Luis Torres

UNITED STATES
CANADA
MEXICO
© Luis Torres


Learning Objectives

The learner will:
  •  recognize that caterpillars are the juvenile life stage of butterflies and moths
  •  understand that insects, including butterflies and moths, grow by moulting
  •  describe some defensive adaptations in caterpillars
  • cultivate an interest in the natural sciences

Teachers' Centre Home Page | Find Learning Resources & Lesson Plans