Platarctia parthenos
St. Lawrence Tiger Moth
(Harris 1850) Arctia parthenos

The first time I saw this species was in Lochabar Mines, Nova Scotia, (probably 1999). Derek Bridgehouse and I were after Hyalophora columbia, and a large female flew into one of our mercury vapour lights.

The moth is fairly widely reported in Maine (quite common, Ron Gatrelle) and upstate New York, and probably flies throughout the Maritime provinces westward to southern British Columbia. I was pleasantly surprised to see one in Montague, Prince Edward Island, July 16, 2005. The image to the right shows the moth with some wing damage after being in a paper bag for six days.

In the United States, The St. Lawrence Tiger Moth is also sporadically reported in Washington, Oregon, Idaho, Montana, Wyoming, Colorado, western South Dakota, Utah, Arizona and New Mexico, with an occasional sighting in northern Michigan.

Joel Szymczyk writes, "This moth is well known from interior Alaska, too."

The large female, depicted above, was put into a brown paper sandwich bag to see if she would oviposit. Pale blue-green, spheroid eggs were deposited in several large clusters on the sides of the bag. I was intrigued by the relatively large size of this Arctiid species (wingspan 7.3 cm, almost three inches) and wish to see the larvae and how big they grow. I can't see how I have missed them as larvae with the eggs being laid in such large clusters. It is possible that the report the larvae feed on woody plants is in error.

On July 26, a black micropyle was noticed on eggs that had darkened considerably to grey. The first cluster of eggs hatched the next day.

Tiny larvae, dark grey, "fuzzy" with black heads, consumed their egg shells and remained enmasse on brown paper. I gently dusted them off onto foliage of various weeds/trees. Larvae were not very clingy and curled into little "puff balls" as they fell onto foliage in little plastic tubs.

Larvae accepted just about whatever I offered from white birch to dandelion. They feed from undersides of foliage and skeletonize leaves, leaving the tougher veins only.

On August 2, it is apparent larvae are very dull grey-yellow with black heads, a black ring probably on the first abdominal segment and a second black ring probably on the eighth abdominal segment.

Larvae are reported to feed on woody plants: Alnus (alder), Betula (birch) and Salix (willows), and they have been reared in captivity on Lactuca (wild lettuce).

Somewhere I read that the larvae take two years to develop, but the same website indicated these moths were seen only in even numbered years. Thus my sighting and capture in 2005 indicates an anomaly or an error in speculation.

If you have experience rearing larvae of this species, please contact Bill Oehlke.

August 20: Larvae are in third instar, and I still have them indoors in plastic tubs. Dandelion foliage does not keep very well so I will attempt to get an outdoor cage built for them on Monday, August 22. Larvae are only about 6.5mm long and show same pattern as second instar. The scan makes then appear darker than they are to the naked eye. Second instar shedded skin remains to the left of larva. Larvae immediately curl into a ball when disturbed. The head is still black.

Matthew Arey writes, "Hi Bill,

"I have had some past success rearing larvae of Platarctia parthenos. In 2003 I collected a wild female with eggs via blacklighting in Harrington, Washington County, Maine. This species is common there in July. I used leaves of Dandelion (Taraxacum), Plantain (Plantago) and Goldenrod (Solidago). The larvae seem to prefer the Dandelion, especially the early instars. They are, however, tricky to rear as more than half succumbed to some sort of infection from an unknown fungus or bacteria.

"I suggest not overcrowding after the third instar and clean out frass from containers often. I have had a similar situation rearing Arctia caja last year. They will spin a loose silken cocoon among dry leaves or paper towels."

Good Luck!

Zdeno Lucbauer writes,

"Hello Bill,

"I have experiences with European Arctids - Arctia caja, A. villica, R. purpurata...

"Here, in Slovakia and I think in all Europe, we have Arctids that winter diapause in larvae stage.

"The first time (to the winter) the rearing is very easy, like a normal breeding.

"But problem is in overwintering.

"The best way is breed them from the eggs in wild, somewhere outdoors. You can make for them vivarium (not glass, but with airy net with a small mesh).

"Inside you plant any food for them as many species are polyphagous. This way you won't have a problem with overwintering, only success and without effort !!!

"I breed like this almost all species of Butterflies and moths."

Good luck !!!

I will probably start them indoors and rear on cut food for a couple of weeks and then move them to an outdoor screen cage over a large bed of transplanted dandelions and plantain.

I will also move lots of dried leaves to the cage when weather gets cold.

I will also try some on some of the woody plants in sleeves to see what they might accept and then overwinter outdoors in a screened cage.

Many thanks to those who have sent suggestions.

I will continue to post here as things develop.

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