Monday, May 21, 2012

The Wonder of Miller Moths

Okay, maybe I'm over the top here, but I find this fascinating....

Those nondescript little brown moths that have been so numerous this spring?  The miller moths?  Turns out they have a life cycle almost as interesting as monarchs - they are just not as pretty and they are definitely more pesty.  (Yes, I know that's not a word, but it should be.)

Most of the miller moths we have been seeing this spring are adults of the army cutworm (Euxoa auxiliaris), a well known pest of wheat and grass, as well as of newly planted tomatoes, beans, peppers, etc.  They'll be disappearing soon though, if they haven't already, because in late spring this year's adults fly west from here into the mountains of Colorado and feed all summer long on the wildflowers there.  (You think the millers are a nuisance here?  Can you imagine having all of Kansas's and eastern Colorado's millers fly through your area each spring?)  These newly hatched adults are in a non-sexual phase;  they don't mate and lay eggs at this point in their life cycle - they are simply storing up energy to do so later.

In late summer and early fall, the millers will return to the plains and lay their eggs in areas of weedy and overgrown vegetation.  While the larvae eat grass and similar plants (like wheat), they actually prefer eating broadleaf plants - which is why the female usually lays her eggs in weedy areas. 

The eggs hatch and the larvae (caterpillars, now called cutworms) eat as long as they can before the cold of winter sets in.  As the weather warms up in the spring, the cutworms begin to eat again until they reach pupating size.  The adult emerges a few weeks later.  And the cycle repeats.  There is only one generation each year.

A couple other cool facts that I learned....

The adult moths are called millers because the scales on their wings come off very easily and reminded early settlers of the flour dust that covered the clothes of grist mill operators.

Millers (the adult moths) are an important part of bear diets during the summer in the mountains.  Each bear can eat up to 40,000 moths/day, which they seem to treat almost like popcorn.  The moth bodies are up to about 70% fat, so it is a great source of calories for the bears.  (This makes miller moths richer in calories, by weight, than elk or deer.)

Other natural predators include birds, toads, predatory ground beetles and bats.

So when you see those dull brown moths fluttering around your lights in the spring or find that little "C" of a caterpillar curled tightly at the soil surface, give it a quick salute for it's audacious life cycle...before you squash it or feed it to the birds.


Gardener on Sherlock Street said...

They are fascinating while being a nusance. When they took flight in the evenings this spring, They made so much noise in the garden I had to go see if it was raining. It wasn't. Sigh. Still finding them in place when I garden.

Gaia Gardener: said...

Wow, GonSS, you had even more than we did. I think I'm glad that I'm not in eastern Colorado this year!

Unknown said...

We are suffering an infestation inside our house in California! What's up with that? No broken windows or screens...they are staying mostly in just one room.