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You’ve all seen them—the giants of the treetops: those enormous caterpillars
we see each fall. Home owners often question whether they’ve put too much
pesticide out and created mutant caterpillars! The large frass pellets
of late instars alert you to the caterpillars’ whereabouts. Although these
caterpillars have been feeding in the treetops all summer, home owners
grow concerned when the giant caterpillars descend from the treetops, causing
the tree’s branches to shake uncontrollably as they make their way to the
mulch to pupate. Is there need for concern? Not really; the caterpillars
have been feasting all summer, but we just haven’t been able to see them.
Your clients will appreciate knowing what these critters are. Don’t encourage
them to bring the cocoons inside—they probably won’t develop properly.
Just tell them to watch and wait for the emergence of the corresponding
giant moths that will appear next spring.
Cecropia Moth
The 4-3/8-inch, sea green cecropia moth (Hyalophora cecropia)
caterpillar has prominent "knobs" on its back: the thoracic knobs are orange,
and the abdominal ones are yellow. The sides of the body have pale blue
knobs (Figure
1). This caterpillar prefers maple (Acer spp.) and cherry (Prunus
spp.) but will feed on many other broad-leaved trees and shrubs, and even
coniferous species such as larch (Larix spp.). This caterpillar
is found east of the Rocky Mountains and in southern Canada. There are
two or three generations in southern parts of the range but only one in
the northern limits. The moth is dark gray-brown with white crescents,
crimson cross bands, and lilac wing tips.
Luna Moth
The caterpillar of the luna moth (Actias luna) is bright green
with pink or black spots and numerous short, pale hairs (Figure
2). This colorful, 3-1/8-inch caterpillar sports eight yellow stripes
on its abdomen. The spiracles are pink or red. It feeds on many forest
trees in the eastern United States and Canada. It typically goes through
three generations per year in the southern and two in the northern part
of its range. The moth is a beautiful light green with small eyespots.
It sports long green "tails" on its hind wings (Figure
3).
Polyphemus Moth
The 3-1/2-inch caterpillar of the polyphemus moth (Antheraea polyphemus)
looks very similar to the luna moth larva: plump, bright green with yellow
bands and red or silver spots (Figure
4). The caterpillar eats leaves of many trees including alder (Alnus
spp.), basswood (Tilia americana), birch (Betula spp.), elm
(Ulmus spp.), hickory (Carya spp.), and sycamore (Platanus
occidentalis). The moth has a 5-inch wingspan and is light brown with
large, yellow and blue eyespots on the hind wings. Its range is throughout
the United States, southern Canada, and northern Mexico. Two generations
a year occur in the southern and one in the northern part of its range.
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International Society of Arboriculture
