Caterpillars

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Caterpillars are the larvae of butterflies and moths. Many are major pests but several merely make us curious as to what they are doing. There are many types of caterpillars and they feed in or on a broad array of trees and shrubs. Some are simple leaf feeders and others bore in tips or are leafminers (see leafminer section). Most feeding by caterpillars takes place in the later instars as they approach maturity. Small caterpillars are easier to control.

  Geometrid larva

Measuring worms or canker worms, geometrids, feed on a wide array of plants. They are like loopers but only have one pair of prolegs on the abdomen. Many are colored like their background and are difficult to see.

    Mourning cloak butterfly adult

These are one of the first butterflies out in spring. Their black wings with the yellow stripe make them quite distinctive.

    Mourning cloak butterfly larva

The caterpillar of the mouring cloak is black and has branched black spines with orange spots on top and orange legs. They feed on willows, elms, and poplars.

Under Construction   Dagger moth larva

These caterpillars are easy to distinguish with their thick coat of white or light yellow hair and black pencils of hair. They feed on willow, apple, boxelder, maple,and oak.

  Swallowtail butterfly adult

Swallowtail butterflies are beautiful and easy to tell with their yellow and black color and the long "tail" on the end of the hindwing.

  Swallowtail larva

Swallowtail caterpillars are brightly colored and the western swallowtail is pale green with brown head and small orange tubercles. They have a pair of retractable orange scent glands just behind the head. Swallowtails can feed on any rosacious plant, alder, willows, fruit trees, etc. depending on species.

  Young swallowtail larva

The very young swallowtail caterpillars resemble bird droppings to help protect them from being eaten.

  Fall webworm larvae

Fall webworm larvae are light colored with long hairs on the body and two rows of black tubercles on the back. They feed on almost all ornamental and shade trees except conifers.

  Fall webworm nest

The nest of the fall webworm is almost always on the terminal end of a branch. When disturbed inside, the larvae make jerky movements in rhythm with each other.

  Western tent caterpillar larva

Larvae of the western tent caterpillar are colorful blue, black and orange caterpillars with tufts of long light colored hair. They hatch from an egg mass on twigs and make tents from which they forage onto the tree for food. They feed on many woody ornamental plants and trees.

  Douglas fir tussock moth larva

Larvae of the douglas fir tussock moth are hairy with orange spots, four median and one posterior white tuft and two long anterior and one posterior long black tufts of hair. They feed on a variety of conifers and defoliate the top third of trees first. There can be large outbreaks of this pest.

  Spruce budworm larva

In Idaho these caterpillars like to feed on spruce and subalpine firs. In spring they first feed on vegetative buds and then on new needles and shoots. They are characterized by having a pinkish brown color with rows of white spots along the sides.

  Pine tip moth larva

These small caterpillars attack many conifers in Idaho landscapes. The larvae first feed in the base of the needles and then bore into the center of new shoots. Mined needles turn red and drop off.

  Damage by tip moth

Trees damaged by tip or shoot moths can take on a reddish hue as the tips are killed. Look for yellow needles near tips of twigs and pitch around new bud clusters for signs of early infestation.

  Leafroller caterpillar larva

Many small cream to green colored caterpillars roll and/or tie leaves together where they feed inside. These leafrollers are generally early season pests but can persist through the summer.

  Leaves tied together by leafroller

Oftentimes after feeding is complete, the caterpillars will pupate inside the rolled up leaves.

  Painted lady butterfly larva

Caterpillars of the painted lady butterfly belong to the thistle caterpillar group. They feed on many plants and weeds. The larvae can be dark brown to black, shiny, and with light stripes on the side and branched spines on top.

  Painted lady butterfly adult

Painted lady butterflies are one of the most common butterflies. They migrate into Idaho from Mexico and Arizona.

  Snail case bagworm case

Snail case bagworms occur in southern Idaho and feed on various annuals and shrubs. They make a small cirlular feeding scar and are found most of the time after feeding as they climb up posts and buildings to pupate.

  Apple and thorn skeletonizer larva

Larvae of the apple and thorn skeletonizer are another type of leafrolling caterpillar. It feeds on birch, crabapple, willow, and mountain ash. They tie a leaf together at the base making it form a cone in which they feed. They eat the green chlorophyll layer off the the leaf making it turn brown and fall off.

  Polyphemus moth larva

These beautiful large green larvae are the immature form of the polyphemus moth. They feed on a variety of trees and are usually not seen until almost full grown. Elm, maple, poplar, and willow would be host trees in Idaho.

  Satin moth larva

Satin moth larvae are one of the tussock moths. They feed on poplar, willow, and other roadside trees and can be quite numerous in certain years. They hibernate as small larvae in bark crevices so are ready to eat when it warms up in the spring.