The Moth Trap

by Eva Amsen

A while ago I kept seeing weird little brown insects flying around. They didn’t really bother me, and the cat had fun catching them, so I let them be for a while. When I found a dead one on the floor one day I decided to see if I could figure out what it was. With the dead bug on my desk I searched several insect websites and typed random descriptions of it in Google. It took me about thirty minutes to figure out that it was not a type of fly, and another twenty to match it up perfectly with a description of a webbing clothes moth.

Oh no, they are secretly eating my clothes! Suddenly they were bothering me, and I wanted them out!

I knew that moth balls would definitely kill them. They contain naphthalene or paradichlorobenzene — enough to do in any moth. But they smell, and they can be toxic to non-moths as well. Now, I wasn’t planning on sniffing moth balls, but my cat would love those little toys, and she also eats any dead moth she finds. No moth balls in my house, that was the plan.

Alternatives to moth balls are cedar wood and pheromone traps. I bought some cedar to put in the box with winter sweaters, and bought a pheromone trap at Grassroots.

This trap is a cardboard house with glue on the inside, and a pheromone lure in the middle. The lure attracts male moths, and the idea is that they get trapped and this will eventually stop them from breeding.

The pheromone trap works. It’s trapping moths. But since April I only trapped 10 moths. There are bursts of activity, in which I catch a few in a row, and quiet times in between. The lure is still working, because one of them flew in quite recently.

What worries me is that moths lay 100-300 eggs, and I only caught 10. On top of that, I’m catching adults, while the larvae are the ones that do the damage, and they might still be around. I don’t know where they are! My clothes look fine. They might be in a rug or a curtain. Who knows!

Even more worrying is this paper that says that male moths are more attracted by pheromones from a nest than by female sex pheromones. I think the lure has sex pheromones, not nest pheromones. A lot of moths hang around in the bathroom. Is that where the nest is? There is less fabric there than anywhere else in the house, so it seems stupid to me, but then again, so does flying into a house with glued walls just because a little lure smells like female moth.

Getting more cedar chips is the next course of action, but cedar works by making male moths unable to smell pheromones, and that might interfere with the moth trap! So the cedar should be close to my clothes or where I suspect the nest is (in the bathroom?), but not close to the trap.

Taxonomy, chemistry, biology, scientific literature, experimental setup… All this for a common household problem, and nothing I did was particularly geeky (except maybe identifying the insect and looking at scientific literature to read about moth pheromones.) I could write a thesis on this. Or at least a proper lab report, with goal, hypothesis, methods, conclusion, discussion, references, and suggestions for further experiments. Actually, I did that just now – see it?


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Don Watcher June 21, 2007 - 3:25 PM

Don’t you need a control, maybe a similar shaped cardboard tube with no pheromones? This would prove that the moths are not simply attracted to the cardboard tube, or something like that.

Shelley June 21, 2007 - 11:22 PM

Which just means you need a research grant. An equipment grant at least (we won’t push for a living stipend at this early stage). Who’s up for buying Eva another moth trap?

Eva June 21, 2007 - 9:59 PM

I guess I do, but they’re $19.95, and research funding for the Moth Trap project is $0…

Maria June 22, 2007 - 10:56 AM

OMG, moths! The deathtrap of knitters!!

Pheromone June 9, 2009 - 3:45 AM

I see that this is an old post. How did it all turn out? Who won you or the moths?

Eva June 9, 2009 - 8:14 AM

Good question! I’ve been meaning to write an update.
Things got worse before they got better. The trap did attract lots of moths, but they never really went away. I just had more and more moths. Earlier this year (about 18 months after the infestation started) I cleaned EVERY SINGLE items of fabric in my house. I found several nests. One was in a T-shirt that I had only washed a week earlier, so that was the height of the infestation! I also found a nest in a cupboard that didn’t have natural fibers in it – or so I thought… There was a nest in a fluff of cat hair that had drifted to the back of the cupboard.

I threw out lots of clothes, washed EVERYTHING, kept plush toys in the freezer for MONTHS. Eventually I did buy moth balls so I could put some clothes in a storage container without fearing that there was still a moth egg in it. Only one sweater got destroyed, but MANY, many, many things has eggs or larvae on them. I had to wash the cat’s toy mice, the living room curtains, a plush fridge magnet…

The moths are pretty much gone now. I used to see 20 a day fly around, and now I see one a week or so. Washing every single thing in the house seemed to have done the trick.

Pheromone June 30, 2009 - 10:07 PM

Good to know, I have never had such a thint happen with moths. Though we did go through a mite infestation one time.

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