Worn-down Grass Veneer Moth
This moth was at our porch light on September 1, 2025. I suspect that it is probably the same species as the one I posted way back on 2012/09/01/, except that one was a lot more pristine. In particular, this new one has the bald patch on its thorax that one frequently sees on old moths, and the trailing edge of the wings looks a bit rough and tattered. That previous one was also found about a month earlier in the year, suggesting that the adults of this species last for at least a month before they lay eggs and die.
The big brushy structure sticking forward out of the head isn’t the antennae (those are the threadlike structures folded over the back). They are actually the maxillae, which in most insects are appendages around the mouth that help to stuff in food. Kind of like if there were fingers at the corners of our mouths. In this case, though, I don’t think they are being used in feeding. They have so much exposed surface area that it is hard to think of what they could be used for other than as additional sensory area to supplement the antennae.
So at any rate, it is either the Vagabond Crambus, Agriphila vulgivagellus, or one of its close relatives. Their larvae eat grasses, and they can apparently be a serious problem with sod and turfgrass. Which is why Colorado State has a fairly extensive information sheet about them here:
https://webdoc.agsci.colostate.edu/bspm/2016/upload/Brighton/Vagabond.pdf
Part of the issue with them in lawns is that they eat the grass themselves, but on top of that, they burrow down into the sod during the day. And then, when blackbirds show up to eat them, they tear up the lawn in the process.
They aren’t an issue for us, because we don’t put in any special effort on our lawn other than mowing it from time to time (and probably half the plants in our lawn aren’t even grass). But I can see where they would be a real problem if you were a commercial producer of sod for landscaping, or if you were trying to maintain that dense, green, uniform growth that golf courses want.