Cycnia Tiger Moth

2012 June 2

This rather elegant white moth with light-brown wing edging was on our house siding on June 1, 2010.

Brandon Woo on BugGuide pointed me to the Cycnia genus of tiger moths, which certainly does look likely. As for which one, it is really too bad that I didn’t get it to spread its wings so that we could see the abdomen, because several members of this genus have bright orange abdomens with black spots. Unfortunately, even this side shot doesn’t show the abdomen.

We can zoom in a bit on the head, though, and from the threadlike antennae, I’d say it’s a female.

There is one other feature that I think might be useful for ID: there appears to be a black stripe running the length of the top of each leg.

Given what I can see of it, I think the closest match is probably the Delicate Cycnia, Cycnia tenera. These have the black-striped legs, the right amount of brown on the leading edge of the wings, and their white abdomens are at least consistent with what I can see here.

If that is the right species, the larvae are known to eat milkweed and “Indian Hemp”, both of which are toxic plants (Indian Hemp can cause heart stoppage if eaten!), so it is a pretty good bet that these moths are probably downright foul (and maybe dangerous) to eat.

It seems that the males make ultrasonic clicking sounds when they are being zeroed in on by bats. There is a theory that the clicks are to jam the echolocation of bats, but this hasn’t been confirmed, and it is equally likely that the clicks are to warn the bats that this moth really isn’t anything that they want to eat. Although these two things are not mutually exclusive, so it could be both jamming and warning at the same time. Anyway, the white color is probably warning coloration (it sure isn’t camouflage!), but that would be of only slight benefit to a night-flying moth because the bats don’t hunt by sight. The ultrasonic warning clicks would be much more to the point.

When not being hunted by bats, they evidently also use the clicks to call to the females. Although the females don’t have particularly good hearing, so this is probably a side-use of the clicks and not their main purpose.

One Response
  1. June 4, 2012

    She looks good in white! 🙂

Comments are closed.