Two Spectacular Tiger Moths: Arctia caja and Arctia parthenos

Arctia caja, great tiger moth, and Arctia parthenos, St. Lawrence tiger moth, are moths in the Family Erebidae, subfamily Arctiinae, which includes these previously discussed moths: Lophocampa maculata, Halysidota tessellaris, Pyrrharctia isabella, Apantesis williamsii, Apantesis virgo, Apantesis phalerata, and Haploa contigua.

Arctia caja and Arctia parthenos are strikingly beautiful moths, as showy as any butterfly, which are just day-flying moths anyway.

Description

Arctia caja is a large moth with a wingspan of 27-32 mm. The forewings are brightly colored in white and brown, forming a mosaic pattern. The underwings are orange-red and marked with large, round to slightly irregular black discal, basal, and submarginal spots containing metallic blue scales. The abdomen is orange-red but darker than the underwings. (Sources: Moths of North Carolina, Pacific Northwest Moths, BugGuide)

Arctia parthenos is also a large moth with a wingspan of 28-33 mm. Its forewings are chocolate brown, marked with numerous pale yellow or cream-colored spots. The underwing is orange with irregular black markings. The abdomen is dark brown to black with orange sides and tip. (Sources: Moths of North Carolina, Pacific Northwest Moths, BugGuide)

Habitat

Arctia caja occurs in northern hardwood forests, conifer forests, wet meadows along creeks and rivers, in disturbed agricultural areas, gardens, and in urban areas. (Sources: Moths of North Carolina, Pacific Northwest Moths, BugGuide)

Arctia parthenos also occurs in northern hardwood forests, conifer forests, boreal mixed woods and parklands, moist shrubby arctic tundra, and mountains in the south. (Sources: Moths of North Carolina, Pacific Northwest Moths, BugGuide)

Host Plants

Arctia caja is polyphagous and feeds on many kinds of herbaceous plants as well as some hardwoods. (Sources: Moths of North Carolina, Pacific Northwest Moths, BugGuide)

Arctia parthenos is also polyphagous but has a preference for hardwoods such as willow, aspen, and alder. (Sources: Moths of North Carolina, Pacific Northwest Moths, BugGuide)

Range

A neighborly moth

Genus overview

Haploa is a genus of moths in the superfamily Noctuoidea, family Erebidae, subfamily Arctiinae (Tiger and Lichen Moths). The genus comprises six species in North America north of Mexico and is not known from anywhere else. Four species are known from Minnesota: Haploa contigua, Haploa lecontei, Haploa reversa, and Haploa confusa.

So that’s the easy part. When I look over my photos of Haploa species, I am struck by the way Haploa lecontei, Haploa reversa, and Haploa confusa seem to grade into one another. Why? Maybe because I am misidentifying them. Or maybe because these are just photos of one species and its range of variation. Which species? I’m not sure anymore, but it might be Haploa confusa. The one I am sure of is Haploa contigua.

Haploa contigua

Haploa contigua is one of four species of Haploa with all white hindwings. The base color of the forewings is cream-colored to white. The costa and inner margins are bordered in dark brown. A diagonal dark brown line extends from the costa beyond the midpoint to the inner margin above the anal angle. Joining this is another line running from the outer margin. Haploa contigua lacks any lines or spurs in the antemedial portion of the forewing. All-white individuals are indistinguishable from other Haploa species with all-white forms.

Haploa contigua inhabits mesic woodlands to riparian woodlands. The larvae feed on the leaves of many species of woody and herbaceous plants.

The genus name “Haploa” is from the Greek word for “simplicity, singleness”, and the species epithet “contigua” is from the Latin word for “bordering” and so the neighbor moth.

Greetings from two tiger moths

*Apantesis phalerata* (Harnessed Tiger Moth). The pectinate antennae indicate this is a male. Photographed on June 25, 2022.

In an earlier post, I wrote about Williams’ tiger moth (Apantesis williamsii). In this one, I present two more Apantesis species: Apantesis phalerata (Harnessed Tiger Moth) and Apantesis virgo (Virgin Tiger Moth).

Most Apantesis moths are characterized by dark forewings and numerous, often parallel, crisscrossing white or off-white lines. The patterns are usually distinctive enough to determine species, but not always.

What’s in a name?

The genus name Apantesis is from the Greek word “apantēsis”, translated as “meeting, an encounter/reply” and “to meet face to face“. It describes a custom of meeting visiting dignitaries where citizens would gather to welcome and escort the dignitary or hero in a procession. I’m not sure why this word was used to name the genus.

Harnessed Tiger Moth (Apantesis phalerata)

Harnessed Tiger Moth (Apantesis phalerata) is part of a group of similar species that includes Apantesis nais, Apantesis carlotta, and Apantesis vittata. Characteristics of the forewing pattern overlap in all four species, making accurate determination difficult, if not impossible, from a photograph. Had this moth spread its wings, exposing the underwings, then the choice might have been between Apantesis phalerata and Apantesis carlotta. Or maybe not.

Genital dissection is considered to be the only reliable way to determine these Apantesis species accurately, but I’m not willing to chop up a moth that rarely gets this far north. I’m just going to call my moth Apantesis phalerata because it looks more like identified specimens than it does the other three species. Additionally, the orange thorax appears to be another characteristic in photos of moths identified as Apantesis phalerata, distinct from the other three. Of course, I could be completely wrong.

*Apantesis virgo* (Virgin Tiger Moth) showing the underwings. The pectinate antennae indicate this is a male. Photographed on July 22, 2019.

Virgin Tiger Moth (Apantesis virgo)

Identifying Virgin Tiger Moth (Apantesis virgo) is not as fraught as it is with Apantesis phalerata. Apantesis virgo is a large white, black, and red moth, 20 to 27 mm long. Black in color, the forewing has distinct off-white veins and transverse lines in the postmedial and subterminal areas. The hindwing may be bright pink, red, orange, or occasionally yellow, with an antemedian and outer margin lined with a row of black spots. There is also a patchy marginal band.

Larvae and host plants

Larvae of Apantesis moths are similar in appearance. Black and bristly, Apantesis virgo larvae have orange-brown spiracles; the setae beneath the spiracles may be orange. Brown to black bristles cover the black larvae of the Apantesis phalerata, which frequently have a pale dorsal line. Larvae of both species feed on low-growing herbaceous plants.

Range and distribution

The following two maps from the Moth Photographers Group show the range and distribution of Apantesis virgo and Apantesis phalerata.

Finding Williams’ Tiger Moth in Minnesota

William's tiger moth on a gravel road in northern Minnesota — **The Williams’ Tiger Moth (*Apantesis williamsii*) I found in the SNF. Photographed on July 20, 2018.**

In a previous life, I searched for and documented rare plant species. But I was always curious about everything in nature, so I made it a point to learn as much as I could about all the things in the forests, glades, lakes, and swamps I explored. Sometimes I would make an interesting discovery, like the moth in the above photo.

I find a new moth

A few years back, while on a rare plant survey, I found a tiger moth that I later identified as Apantesis williamsii (Williams’ Tiger Moth). I found the moth in Cook County, Minnesota, in the Superior National Forest (SNF). It was simply lying in the middle of an old logging road just waiting to be found, I guess.

I’d never seen a moth quite like this one. I photographed it (I would have anyway no matter if it was new to me or not) and took some notes about the surrounding area. Then I GPS-ed the location, which is about 20 miles south of the US-Canadian border.

Because blueberry pickers were using the road that day, I carefully moved the moth to a safe spot. Then I got back to that day’s mission, searching for rare plants in the forest and the rare Nabokov’s blue butterfly (Lycaeides idas nabokovi). It might have been in the area as its larval host plant, Vaccinium cespitosum (dwarf bilberry), grew nearby in a prescribed burn. I found plenty of dwarf bilberry that day, but no sign of Nabokov’s blue butterfly. Not even a caterpillar.

Not a common species in Minnesota

Apantesis williamsii is uncommon in Minnesota. It appears that there are only two records before 2018. One record is from Cook County, the same county where I found this one, up in the northeastern corner of the state. The other is from Lake of the Woods County in the Northwest Angle, right on the US-Canadian border, found in 2017.

Since then, additional sightings of Apantesis williamsii have been made. Two other sightings (here and here) were made in Minnesota in 2018, but from northern St. Louis County, about 50 miles west near Ely, and also close to the Boundary Waters and Canada.

***Apantesis williamsii* range map. The distribution of ***Apantesis williamsii***** **is concentrated in the Cordillera.**

Globally secure

This is not a rare species globally, but based on the small number of sightings, it appears to be uncommon in Minnesota. Most records of Apantesis williamsii are from the Cordillera, starting in Saskatchewan, Canada, and then south through Montana, Idaho, Wyoming, Colorado, Utah, California, Nevada, Arizona, and New Mexico in the western US. It occurs sporadically elsewhere, with scattered reports from Alberta, Manitoba, Ontario, Quebec, and New Brunswick in Canada, and in Michigan and Maine in the US.

Habitat preferences

In the main part of its range, Apantesis williamsii can be found in mountain meadows at middle to high elevations. It also occurs in quaking aspen forests and dry coniferous forests with sandy soil. The latter isn’t too different from the site where I found it. This was in a forest of aspen, birch, spruce, and fir with some jack pine and white pine on sandy soil. The weather is also cool in the summer, although climate change may upend that.

What does it it eat?

Larval food plants of Apantesis williamsii are not known, but it may feed on low-growing herbaceous vegetation like other species of Apantesis.