Some days I go out into my yard looking for a new species to chronicle in this blog. On other days, I just happen to run across interesting species serendipitously. On June 8th, I was out building a new shed when my son called me over to look at a moth that he found sitting on a piece of plywood we had lying on the lawn. It turned out to be a Northern Pink-striped Oakworm Moth (Anisota virginiensis virginiensis).
Moth or Butterfly?
It was one of the most colorful moths I had ever seen. Remember the checklist of butterfly versus moth traits I used to help identify the skippers (Hesperidae Family) last July? This one is not nearly as tricky as the skippers.
It has broad, feathered antennae, a large head, a thick, hairy body, and holds it wings flat and swept back while at rest. The bright colors and the fact that it was out and about during the daytime are the only traits which might suggest butterfly, but the others are far more accurate indicators. So we can be sure that it is a moth.
There are many, many species of moths and I certainly don't know them all or even a large percentage by sight. This one was knew to me, but was reminiscent of the Rosy Maple Moth. The Rosy Maple Moth is member of the taxonomic Family Saturniidae (Saturn Moths or Giant Silkworms and Royal Moths). Therefore, I started looking for a match at the Family level.
In reviewing images of the Rosy Maple Moth, I saw several photos of its larval form at bugguide.net and in my Audubon Field Guide. I recalled having seen a very similar early instar caterpillar on some oak leaves very near where this caterpillar was found. Perhaps then, instead of a Maple Moth it was some kind of Oak Moth. Using the search term "Oak Moth Saturnidae," I was able to find the Pink-striped Oakworm Moth (Anisota virginiensis), which has three sub-species.
Sub-species of Anisota virginiensis
The sub-species are most easily differentiated by the regions in which they live. In New Hampshire, we'd expect to find the sub-species Northern Pink-striped Oakworm Moth (Anisota virginiensis virginiensis). The Southern Pink-striped Oakworm Moth (Anisota virginiensis pellucida) lives from South Carolina to Florida and west to Louisiana according to Bugguide.net. While the Texas Pink-striped Oakworm Moth (Anisota virginiensis discolor) is found, as you may have guessed, in Texas.
Sexual Dimorphism
We know the species, and because the species, like human beings, is sexually dimorphic (the males and females look different), we can tell that the specimen I found in my yard is a male. Size is a key differentiator. The female is significantly larger than the male, but without one of each sex to compare, and without a tape measure handy, this is difficult to determine.
Hyaline Area
The other key trait used to determine the moth's sex is that males have a large clear "window" on the forewing (the larger wing on each side). You can literally see right through this part of the male's forewing. This is called a hyaline area. The female has no such clear patch.
Starvation Diet
Normally, I'd include dietary information in the Quick Facts section, but this one's pretty interesting. The larva of the species, called simply the pink-striped oakworm, eats oak leaves. If present in large numbers they can do consider damage to a tree's foliage. When they metamorphose into adult moths, however, do not eat at all according to butterfliesandmoths.org. Once they pupate, they begin to slowly starve to death as the stored fats retained from the caterpillar stage are used up.
Diurnal or Nocturnal?
I've already said the specimen of this moth that I found was out during the daylight hours, and I've identified it as a male. Males frequently fly during the day, seeking females by scent. Females, on the other hand, fly at night to find oak leaves suitable for egg-laying and can be attracted by light traps.
Quick Facts about the Northern Pink-striped Oakworm Moth:
Where does it live? Anisota virginiensis virginiensis ranges from Nova Scotia to North Carolina in the East and from Minnesota to Manitoba in the West.
Where does it go in winter? The Northern Pink-striped Oakworm Moth pupates in late fall and overwinters in the pupa just below ground according to butterfliesandmoths.org.
Habitat: Pretty much anywhere that oak trees are found from deciduous forest to city parks.
When is it here? Anisota virginiensis virginiensis does not migrate and is present here all year round. Its flight season, however, runs only from June to July in New Hampshire according to Bugguide, but as one goes farther south there may be two or even three generations each year depending upon how far south one goes. Of course, these are likely the Southern or Texas sub-species.
Lifespan: Up to one year, but perhaps only a few months in warmer climates.
Notes: Eggs are laid in bunches on the underside of oak leaves. According Forestryimages.org, they are spherical and yellow, laid in batches of several dozen at a time. Each egg is individually attached to the leaf.
Date found in my yard: June 8, 2012
Taxonomy of the Northern Pink-Striped Oakworm Moth:
Kingdom: Animalia (Animals)
Phylum: Arthropoda
Class: Insecta (Insects)
Order: Lepidoptera (Butterflies and Moths)
Family:Saturniidae (Silkworm Moths and Royal Moths)
Genus: Anisota
Species: Anisota virginiensis
Sub-species: Anisota virginiensis virginiensis
 |
| Northern Pink-striped Oakworm Moth, male Photo by Brad Sylvester, copyright 2012. Do not copy. |
Moth or Butterfly?
It was one of the most colorful moths I had ever seen. Remember the checklist of butterfly versus moth traits I used to help identify the skippers (Hesperidae Family) last July? This one is not nearly as tricky as the skippers.
 |
| Northern Pink-striped Oakworm Moth (Anisota virginiensis virginiensis) Photo by Brad Sylvester, copyright 2012 Do not copy. |
There are many, many species of moths and I certainly don't know them all or even a large percentage by sight. This one was knew to me, but was reminiscent of the Rosy Maple Moth. The Rosy Maple Moth is member of the taxonomic Family Saturniidae (Saturn Moths or Giant Silkworms and Royal Moths). Therefore, I started looking for a match at the Family level.
In reviewing images of the Rosy Maple Moth, I saw several photos of its larval form at bugguide.net and in my Audubon Field Guide. I recalled having seen a very similar early instar caterpillar on some oak leaves very near where this caterpillar was found. Perhaps then, instead of a Maple Moth it was some kind of Oak Moth. Using the search term "Oak Moth Saturnidae," I was able to find the Pink-striped Oakworm Moth (Anisota virginiensis), which has three sub-species.
Sub-species of Anisota virginiensis
The sub-species are most easily differentiated by the regions in which they live. In New Hampshire, we'd expect to find the sub-species Northern Pink-striped Oakworm Moth (Anisota virginiensis virginiensis). The Southern Pink-striped Oakworm Moth (Anisota virginiensis pellucida) lives from South Carolina to Florida and west to Louisiana according to Bugguide.net. While the Texas Pink-striped Oakworm Moth (Anisota virginiensis discolor) is found, as you may have guessed, in Texas.
Sexual Dimorphism
We know the species, and because the species, like human beings, is sexually dimorphic (the males and females look different), we can tell that the specimen I found in my yard is a male. Size is a key differentiator. The female is significantly larger than the male, but without one of each sex to compare, and without a tape measure handy, this is difficult to determine.
Hyaline Area
 |
| The lower wing edge is clearly visible through the transparent window of the hyaline area of the male's forewing. Photo by Brad Sylvester, copyright 2012. Do not copy. |
Starvation Diet
Normally, I'd include dietary information in the Quick Facts section, but this one's pretty interesting. The larva of the species, called simply the pink-striped oakworm, eats oak leaves. If present in large numbers they can do consider damage to a tree's foliage. When they metamorphose into adult moths, however, do not eat at all according to butterfliesandmoths.org. Once they pupate, they begin to slowly starve to death as the stored fats retained from the caterpillar stage are used up.
Diurnal or Nocturnal?
I've already said the specimen of this moth that I found was out during the daylight hours, and I've identified it as a male. Males frequently fly during the day, seeking females by scent. Females, on the other hand, fly at night to find oak leaves suitable for egg-laying and can be attracted by light traps.
Quick Facts about the Northern Pink-striped Oakworm Moth:
Where does it live? Anisota virginiensis virginiensis ranges from Nova Scotia to North Carolina in the East and from Minnesota to Manitoba in the West.
Where does it go in winter? The Northern Pink-striped Oakworm Moth pupates in late fall and overwinters in the pupa just below ground according to butterfliesandmoths.org.
Habitat: Pretty much anywhere that oak trees are found from deciduous forest to city parks.
When is it here? Anisota virginiensis virginiensis does not migrate and is present here all year round. Its flight season, however, runs only from June to July in New Hampshire according to Bugguide, but as one goes farther south there may be two or even three generations each year depending upon how far south one goes. Of course, these are likely the Southern or Texas sub-species.
Lifespan: Up to one year, but perhaps only a few months in warmer climates.
Notes: Eggs are laid in bunches on the underside of oak leaves. According Forestryimages.org, they are spherical and yellow, laid in batches of several dozen at a time. Each egg is individually attached to the leaf.
Date found in my yard: June 8, 2012
Taxonomy of the Northern Pink-Striped Oakworm Moth:
Kingdom: Animalia (Animals)
Phylum: Arthropoda
Class: Insecta (Insects)
Order: Lepidoptera (Butterflies and Moths)
Family:Saturniidae (Silkworm Moths and Royal Moths)
Genus: Anisota
Species: Anisota virginiensis
Sub-species: Anisota virginiensis virginiensis
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