Eacles imperialis imperialis
ee-UH-kleesMim-PEER-ee-al-ihs
(Drury, 1773) Phalaena

Eacles imperialis (male) courtesy of Tony Thomas (copyright)

This site has been created by Bill Oehlke at oehlkew@islandtelecom.com
Comments, suggestions and/or additional information are welcomed by Bill.

TAXONOMY: Superfamily: Bombycoidea, Latreille, 1802 Family: Saturniidae, Boisduval, [1837] 1834 Subfamily: Ceratocampinae, Harris, 1841 Genus: Eacles, Hübner, [1819] Species: imperialis, (Drury, 1773)

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DISTRIBUTION:

Eacles imperialis moths (wingspan: males 92-112mm; females: 87-120mm) are found throughout the eastern half of the United States with greater concentrations in Ohio, southern Pennsylvania and New Jersey, and the Virginias. It is also apparently quite common in the southern states from Florida to at least the eastern half of Texas, based on numerous larval images that are submitted from those states.

In Canada there are populations in southern Quebec and Ontario, but in the provinces the species is generally replaced by the smaller subspecies Eacles imperialis pini.

Eacles imperialis male, reared on Quercus robur,
courtesy of Rainer Plontke.

Visit Eacles imperialis form nobilis, a darker suffused form which most often appears in Texas, Louisiana and Alabama. Both forms, didyma and nobilis, originate from nominate imperialis.

Thomas Payne sends the following images from Tennessee. He reports that he sees the didyma form about 8% (1/12 males) of the time that he takes Eacles imperialis at his lights. Note the orange scaling in the pm areas of the wings, particularly the lower wings.

Eacles imperialis male, form didyma,
Tennessee, courtesy of Thomas Payne.

Eacles imperialis female,
Tennessee, courtesy of Thomas Payne.

FLIGHT TIMES:

In the northern half of its range the single-brooded adults are on the wing from June to August. In New Jersey imperialis (males and females) usually came in to lights in July. In the South this species flies from April to October, suggesting at least two broods, but the extended flight season may be due to an irregular emergence pattern. Dirk Bayer confirms there are at least two broods in southern Alabama.

Joel Szymczyk writes, August 9, 2008, "Last night I saw a caterpillar in the glare of my merc light in the back yard. It was obviously Eacles imperialis. It was on one of the ornamental junipers which were planted before I moved here. I pretty much hate those trees and have been seriously thinking about chopping them all down. They are fairly infested with "bagworm" moths, and one tree was completely killed this year by them. Anyhow I was very surprised to see this eating juniper because there are so many decent oaks to choose from.

"Not five minutes later, I saw an adult Eacles hanging in one of the junipers. Definitely a female, and it was ovipositing. This has to be one of the most massive moths in the eastern USA. Cecropia certainly has larger wing area, but the body of this imperialis is just huge. I guess I'll keep the trees, but I have to figure out how to get rid of the bagworms."

ECLOSION:

Adults emerge from underground pupae with most eclosions taking place before sunrise.

Visit Eacles imperialis male, Pickens County, Georgia, August 19, 2009, courtesy of Aubrey Scott.

SCENTING AND MATING

Eacles imperialis (female) courtesy of Tony Thomas (copyright)

The slightly larger female begins "calling" after midnight by extending a scent gland from her abdomen. Smaller males fly into the wind to pick up the scent and track the stationary female. Males have more purple on the shoulders and on the outer regions of the forewings.

EGGS LARVAE, PUPAE

Eggs are usually deposited singly or in small groups of 2-5 on a number of coniferous and deciduous trees. Incubation lasts from 12 to 14 days and the larvae emerge as solitary feeders. Under natural conditions larvae would leave the food plant at pupation time and burrow underground to pupate.

Larvae will pupate without soil if placed in the dark in a warm place. Covered five gallon buckets, lined with paper toweling, make good pupation chambers.

I now use sandwich sized tupperware type plastic containers for pupation. I fold up a full sized, non-secented paper towel and place it in the tub. I put as many as three to five mature larvae in each tub and snap the lid shut. There are no air holes in the tubs that I use. The larvae have adequate air for this process, and diapausing pupae need very little air, so the tubs also serve as overwintering quarters in the refrigerator crisper.

The larvae crawl between the folds of the paper towel or underneath it and usually pupate in three to five days.

Non-diapausing pupae might need an airier environment for prolonged storage.

The next four larval images are all copyrighted and are used with permission only from Tony Thomas. The parent of these larvae was a female from The Great Dismal Swamp on the border of West Virginia and North Carolina.

The first or second instar larva to the left will quickly move away from one to four siblings to become a solitary feeder on oak, maple, pine, sycamore, Sweet gum, or sassafras, the favorite foods of this species. Larvae still do not consume much in the second and third instars, and they have also been reported to feed upon various cherries, sumacs, birches, willows, and ash trees Third and fourth instar larvae become heavy feeders but seldom do damage to the many evergreens (softwoods) upon which they also feed: cedar, fir, (larch/juniper), and pine. The impressive hairs which become prevalent in the last instars are non-urticating. Some larvae of other species have stinging hairs. In most cases the larvae take the green form shown at the end of this section. Steven Stone also reports elm, hickory, hornbeam, chestnut, and privet as foodplants for this highly polyphagous species. The green larval form pictured below is more typical of this species. Mature larva can be either green or brown or some combination of the two, usually with two yellow scoli on the first thoracic segment, two elongated yellow to orange thoracic scoli on each of the next two thoracic segments and a single elongated one on the final abdominal segment. There are also two rows of much smaller yellow scoli, one on each of the other abdominal segments. Courtesy of John A. Weidhaas, University of Vermont

Vist a beautiful series of images of Eacles imperialis larvae, courtesy of Bonnie J. Caruthers.

Ian Mascall has forwarded beautiful images of a third instar Eacles imperialis imperialis larva, from a "didyma" form female. Images were taken by Ben Horton.

Eacles imperialis imperialis third instar, courtesy of non-member Ben Horton,
via Ian Mascall, from didyma form female.

Eacles imperialis imperialis third instar, courtesy of non-member Ben Horton,
via Ian Mascall, from didyma form female.

Eacles imperialis pupa, courtesy of Jurgen Vanhoudt.

Eacles imperialis pupae, courtesy of Jurgen Vanhoudt.

The dimorphic wing coloration of this species is especially evident in this gynandromorph which flew in to a black light in Pottersville, New Jersey, in early July of 1962. My father and I got into an argument over whether it was a male or female until he recognized the bisexual nature of the insect and explained what we had captured.

Larval Food Plants

It is hoped that this alphabetical listing followed by the common name of the foodplant will prove useful. The list is not exhaustive. Experimenting with closely related foodplants is worthwhile.

Abies grandis Acer negundo Acer pseudoplatanus Acer rubrum Acer saccharinum Acer saccharum Aesculus hippocastanum...... Alnus serrulata Betula alba Betula papyrifera Betula populifolia Bursera tomentosa Carpinus caroliniana Carya Castanea dentata Castanea pumila Castanea sativa Cedrus Chamaecyparis thyoides Cochlospermum vitifolium..... Cornus Crataegus Diospyros accharinum Fagus grandifolia Fagus sylvatica Gleditsia triacanthos Gossypium herbaceum Juglans cinerea Juniperus communis Juniperus virginiana Koelreuteria paniculata..... Larix laricina Ligustrum Lindera benzoin Liquidambar styraciflua Myrica cerifera Ostrya virginiana Picea Pinus banksiana Pinus echinata Pinus griffithii Pinus serotina Pinus strobus Pinus taeda Platanus occidentalis.... Platanus orientalis Prunus serotina Prunus virginiana Quercus alba Quercus coccinea Quercus laevis Quercus macrocarpa Quercus palustris Quercus robur Quercus rubra Quercus virginiana Rhus glabra Rhus laurina Rosa Robinia Salix Sambucus canadensis Sassafras albidum Taxodium distichum Tilia americana Tilia europaea Tilia heterophylla..... Tsuga canadensis Ulmus alata Ulmus americana Ulmus procera Ulmus rubra Ulmus thomasii Viburnum dentatum

Grand fir Box elder/Manitoba maple Sycamore maple Red maple Silver maple Sugar maple European horsechestnut Hazel alder White birch White/paper birch Gray birch Torchwood American hornbeam Hickory American chestnut Allegheny chinquapin Spanish/Sweet chestnut Cedar Atlantic white cedar Rosa amarillo Dogwood Hawthorn Persimmon American beech European beech Honeylocust Levant cotton Butternut Common juniper Eastern red cedar varnish tree Larch/Juniper/Tamarack Privet Spicebush Sweetgum Southern bayberry/Wax myrtle American hop hornbeam Spruce Jack pine Shortleaf pine Himalayan pine Pond pine Eastern white pine Loblolly pine American plane tree Oriental sycamore Wild black cherry Chokecherry White oak Scarlet oak Turkey oak Bur oak Pin Oak Pedunculate Oak/English Oak (RP) Northern red oak Live Oak Smooth sumac Laurel sumac Rose Honeylocust Willow American elderberry Sassafras Bald cypress American basswood Common lime White basswood Eastern hemlock Winged elm American elm English elm Slippery elm Rock elm Southern arrowwood

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The pronunciation of scientific names is troublesome for many. The "suggestion" at the top of the page is merely a suggestion. It is based on commonly accepted English pronunciation of Greek names and/or some fairly well accepted "rules" for latinized scientific names.

The suggested pronunciations, on this page and on other pages, are primarily put forward to assist those who hear with internal ears as they read.

There are many collectors from different countries whose intonations and accents would be different.

Some of the early describers/namers chose genus and species names indicating some character of the insect, but more often, they simply chose names from Greek or Roman mythology or history.

Those species names which end in "ensis" indicate a specimen locale, and those which end in "i", pronounced "eye", honour a contempory friend/collector/etc.

I do not know the source of the genus name "Eacles", but it may be a combination of "Ea", the Greek word for gods and goddesses and the Greek suffix "cles", meaning 'glory of'.

The species name "imperialis" is probably for majestic appearance and colouration of this moth.

Visit Eacles imperialis mature larva, The Woodlands, Montgomery County, Texas, November 2, 2009, courtesy of Sophie and Ellie Johnson.