Eacles imperialis
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 Eacles imperialis, adult male
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| Eacles imperialis (Drury, 1773) |
The Imperial Moth (Eacles imperialis) is a Nearctic member of the family Saturniidae and subfamily Ceratocampinae.
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[edit] Range
Imperial moths (their many regional morphs, subspecies and sibling species) range from Mexico to Canada and from the Rocky Mountains to the Atlantic Coast. Nominate Eacles imperialis imperialis has been recorded historically from New England and Southern Canada, south to the Gulf Of Mexico and west across the Great Plains. In modern times, its range has receded northward (where it was always a good find); it is considered common south of the Mason-Dixon line. Subspecies E. imperialis pini occurs in coniferous and transition zone woodlands at the northern edges of the New England and Great Lakes States and northward into Canada. In the southwest, closely related Eacles oslari replaces imperialis, and thence southward into Mexico.
[edit] Status
Eacles imperialis is one of a few saturniid species in a regional decline throughout the northeastern US, with some New England states lacking records for many decades. A colony on Martha's Vineyard, Massachusetts has been the subject of scientific and local political activity, especially concerning preservation of sensitive frost-bottom oak/pine habitat. Reasons for decline are unclear, as is the true northern limits of nominate imperialis' range, due to possible confusion with subspecies pini in existing records. Imperialis is certainly a common species of middle-atlantic states, appalachia, the Ohio Valley and Deep South regions, and is associated with forest, rural and suburban habitat. It is possible that to the north, imperialis requires specific habitat and the increasing fragmentation of niches such as coastal or montane pine barrens is a factor.
[edit] Life Cycle
There is only one brood a year.
[edit] Egg
Eggs are laid on the underside of leaves in clusters of 2-5. They take approximately two weeks to hatch. The day before they hatch, the egg turns from milky yellow to translucent white.
[edit] Larva
First instar lasts generally only a few days. After hatching, the caterpillars tend to wander around before finally settling on eating the particular plant they are on. After a few days, a small amount of silk is placed on the major vein of a leaf. The caterpillar then molts from that position leaving the old exoskeleton behind. Sometimes the shed exoskeleton is eaten. This continues on over most of the instar. Around the third or fourth instar, variation is noticeable. The caterpillars in the third and fourth instar vary from orange to black on the head, spines, body, and feet. In the fifth instar, there are two distinct variations in orange and green form.
[edit] Pupa
As with most of this subfamily, when the caterpillars are ready to pupate, they burrow underground.
[edit] Adult
Adults emerge once a year to mate. In the northern part of their range they tend to emerge mid summer (June - August), while in the southern half they tend to emerge at more varied times (April - October). A linked pair is vulnerable to predators, particularly foraging raccoons.
As with all of Saturniidae, the adults do not feed. Their mouthparts have been reduced.
[edit] Images of Life Cycle
 Imperial moth eggs |
 1st instar |
 1st instar on a pine needle |
 2nd instar |
 3rd instar |
 4th instar |
 5th instar |
 5th instar |
[edit] Images of Adult Imperial Moth
Location: Eastern Pennsylvania (near Philadelphia), July 27, 2007. This specimen is typical of the nominate Eacles imperialis imperialis, from a locality toward the northern end of the species contemporary range.
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[edit] Sexual Dimorphism
Sexual dimorphism is present in this species and all of Saturniidae :-
- The males are generally smaller and show larger patches of purple.
- The females are generally larger, mostly from carrying eggs, and are more yellow.
- The antenna of the male is fibrous.
[edit] Food plants
Larvae feast on a variety of host plants including:
- Quercus (Oak)
- Acer (Maple)
- Liquidambar styraciflua (American Sweetgum)
- Sassafras albidum (Sassafras)
- Pinus (Pine)
[edit] Other information
There is a high amount of variation within this species. The colors of the adult are always yellow and purple but can vary distinctly on this. Generally there is more purple on the forewing and more purple on males. However, one subspecies tends to have a distinct coating of purple over the entire wings.
Darker, heavily mottled individuals are typical forms of the southern and western range and may represent a clinal variation of nominate imperialis. Subspecies pini to the north, and sibling species Eacles oslari to the southwest exhibit similar morphs. Regional foodplant preferences have been noted as well, although captive-bred populations from all sources are nearly omnivorous.
The Imperial Moth is perhaps the only example of such a creature as a character in a novel. Naturalist Gene Stratton Porter's "Girl Of The Limberlost" features imperialis prominently in the plot development, and her account of it's life history in "Moths Of The Limberlost" (a chronicle of her discovery of lepidoptera in early 20th Century rural Indiana)captures not just the science but the charm of the giant silk moths and childhood discovery of nature.
[edit] External links
- Eacles imperialis, Butterflies and Moths of North America
