Over the last week we’ve had an influx of moths in the barn.  I noticed the first one dead on the floor, and then suddenly they were everywhere.  I don’t think I ever saw one alive (they get caught in the barn, and it’s too hot for them to survive long) but I picked one up and took some photos of it.


I had no idea what kind of moth it was, so I google searched for black and brown moths and discovered it was a Parthenice Tiger Moth (Grammia parthenice).  Wikipedia says this kind of moth lives in Southern Canada and most of the United States, except for the west coast.  Obviously this is incorrect, because we are Definitely on the west coast, and we Definitely have this moth (unless I identified it incorrectly, which is totally possible).


While trying to find out what kind of moth my picture was, I found out a whole bunch of interesting information.

Did you know:

Many of the 11,000 species in the family Arctiidae (ark-TYE-ih-dee) are poisonous.  They can retain the toxins from their host plants while in the larval form and they can also acquire toxins by regurgitating on a decomposing plant and then ingesting the fluids (gross but cool).  The adult moth can also transfer the toxins to its larvae and the males will sometimes transfer his defenses to a female protecting its larvae.  They can have quite a few different poisons in them, but two of the most interesting ones are cardenolides, which can cause congestive heart failure, and pyrrolizidine alkaloids, which can cause liver failure!

Luckily, like many other animals, these moths have developed aposematic characteristics, in the form of bright coloration, to deter predators from eating them.  Some nocturnal species have even developed ultrasonic vibrations which confuse predators (mainly bats).

Moths often spread their wings to appear larger and discourage predators (notice the bright colored underwings)
Moths often spread their wings to appear larger and discourage predators (notice the bright colored underwings)

When these moths are in the caterpillar form, they are often referred to as “woolly bears” or “woolly worms” because they are furry.  In Northeastern American lore they are believed to predict the weather.  If the caterpillars are more brown then black, it will be a mild winter, more black then brown and a harsh winter is ahead.  Of course this is only a legend, one female moths’ larvae can vary from all black to all brown and anywhere in between.

Another interesting fact, they can survive extreme cold!  Even into subzero temperatures.  Some species are even known to crawl across snow looking for a place to build their pupa.

It’s good to note, especially since the caterpillars are awfully cute, these moths may be abundant but they rarely do permanant damage to a healthy host.  So if you see a few in your garden, don’t worry.  And anyway, two of their main food sources are dandelions and thistle (weeds we usually want gone anyway!).

Thistle flower

Further Reading:

Butterflies and Moths of North America

Capture a “Bear” for the Winter (fun for kids!  and adults too of course)