Feature Article - for release the week of  April 6, 2008

Dan Culbert - Extension Horticulture Agent

What’s that Bag?

An office visitor brought in a curious hanging thing form their oak tree last week.  It was vaguely familiar to me, but I let our Master Gardeners do the legwork on this mystery.  They came up with an answer which presents an interesting story worth sharing with readers.

The story involves a bit of Greek mythology, a natural self-defense mechanism, a lesson on   dealing with worms on your plants, and a fascinating look at a beautiful creature that may occasionally pop up in our Florida Yards.

A small silk bag

The local gardener that brought in our mystery bag reported that there where a couple of these things hanging around his oak tree.  Okeechobee Master Gardener Terry Lane also reported that she has seen a small number of these containers on the oaks in her Florida yard.   I suggested that it may be some kind of cocoon, so she started her search for photos of insect cocoons, and soon she tracked it down.

An office visitor brought in this specimen from their oak tree for identification.  It is the empty cocoon of an infrequent moth found in Florida yards.  Photos Dan Culbert, UF/IFAS

Polyphemus is a mythological creature mentioned in Homer's Odyssey. This painting was created by  J.H.W. Tischbein in the late 1700's.

It turns out this fuzzy bag is an empty cocoon case for a large moth.   It has the curious name of Polyphemus Moth, Antheraea polyphemus.  (The approximate pronunciation is “Pal-e-FEE-mus.”). The wings have very prominent eye spots that give the moth its name – the one-eyed Cyclops in Greek mythology was named Polyphemus (see figure at right.)

At this time of year in Florida, a first generation of these moths is now emerging from their silken cases.  The fully developed adult secretes an enzyme that helps dissolve a flap in the cocoon, and the emerging adult wiggles its way out. 

Big, Brown and Beautiful

Adult Polyphemus moths may have wingspans of 4 to 6 inches.  The general color is anywhere between red and brown, but there are several unique markings that make these moths distinctive. Males and females look very similar except the male has larger feathery antenna, while the ladies have a larger body to hold their eggs. 

The female Polyphemus  moth (left) has a broader body and thinner antenna than the male moth    Photo: L.L. Hyche, Auburn Univ.	Close-up of hind wing eye spots.  They may remind us of the Cyclops Polyphemus of Greek mythology; they may also scare away a  predator. Photo: Howard Ensign Evans, Colorado State Univ.

The front wings have a small transparent wing spot ringed with light yellow.  When the moth is disturbed, it shows its back wings, which also have eyespots.  These hind wing markings are very noticeable.  The blue-black eyes would certainly scare a predator into thinking they were about to attach a much large creature.

A short while after emerging from the cocoon the adult is ready to find a mate. Female moths secrete a pheromone that attracts males from miles away, and then she spends the next week finding suitable trees to lay single eggs.  Adult moths do not feed at all during their brief final stage of life.  Several generations of these moths can be found in Florida, while in more northern areas two generations per year are more typical.

The adult Polyphemus Moth is a member of the regal moths or giant silk moths.  This family (Saturniidae) includes many large sized moths often with striking colors and shapes.  They attract a lot of attention when they are encountered, especially at night when they bang against a window.  Other Saturn family moths are the lime green  Luna Moth, the yellowish Io moth, and the Cecropia moth, a similar reddish brown adult.

Great big Green Worm

The caterpillar of this moth starts out as a small light brown egg. It hatches into a tiny yellow caterpillar, and will consume 86,000 times its weight in two months. 

They are not picky eaters, and will feed on trees leaves including oaks maples, elms, hickories and willows.  One source even suggested that they would sometimes be a pest on peach and cherry trees; another report said that the Polyphemus caterpillar may eat citrus tree leaves.

Recently hatched Polyphemus caterpillars start out  yellowish in color.  They gradually turn to an apple green color and develop hairy tufts. Photo: L.L. Hyche, Auburn Univ.	Fully grown caterpillars measure about three inches long. Photo: L.L. Hyche, Auburn Univ.

Full grown larvae are thick bodied and can measure around three inches in length.  This species is apple green in color with yellow spots or lines on each segment.  The head is reddish brown in color.  The caterpillars of this moth family have lots of barbs and spines that make them look ferocious, but only one of these, the Io moth caterpillar, actually has stinging hairs.

Is this really a pest?

This insect is found throughout most of North America, and has been reported in many areas of Florida.  There is no “official” sighting of it in Okeechobee (yet), but it has been reported seen in Highlands.  If you can positively identify one in your yard, please let us know so we can confirm its range.

They are not abundant, and rarely can be considered to be a pest because their numbers are not that great.  Occasionally they may damage seedlings or young trees, but they can be picked off and disposed of if they are seen on high value ornamentals.   The use of toxic pesticides to manage these caterpillars would probably not be recommended except in extreme cases.

Parasitic wasps are known to attack the caterpillars, and squirrels are thought to consume the pupa that is found inside cocoons.  Other threats to this moth are the removal of tree braches by pruning and night lights, which can attract adult moths to places where predators or curious people will capture and dispense with the big moths.

 

I’ve placed more information on our Okeechobee web page, http://okeechobee.ifas.ufl.edu/.  If you need additional information on the Polyphemus Moth, please email us at okeechobee@ifas.ufl.edu or call us at 863-763-6469.  Local residents can stop by our office at 458 Hwy 98 North in Okeechobee, and visit our Okeechobee County Master Gardeners from 1 to 3 PM on Tuesday afternoons.  GO GATORS! 

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Trade  names, where used, are given for the purpose of providing specific information. They do not constitute an endorsement or guarantee of products named, nor does it imply criticism of products not named. The Florida Cooperative Extension Service - Institute of Food and Agricultural Sciences is an equal opportunity/affirmative action employer authorized to provide research, educational information, and other services to individuals and institutions that function without regard to race, color, sex, age, handicap, or national origin.  Florida Cooperative Extension Service / IFAS / University of Florida.  Larry A.  Arrington, Dean. Last update: 04/09/2008.  This page is maintained by Dan Culbert