The Moth Trap

What is a moth trap? asked Karolyn Cooper. Well it isn’t the longest running play in the world. Very few people know that Dame Agatha originally intended to call her magnum opus The Moth Trap. Why she changed her mind we’ll never know. Perhaps it was because the answer would have been far too obvious. The lepidopterist dunnit. Not much of a plot there then.

Essentially a moth trap is a light and a container. The idea is that the moths are attracted to a light and then descend into the container which is designed to make it difficult for them to escape. Later on a bleary-eyed moth-er comes along, inspects the catch, records what is there and probably photographs anything interesting. Then the moths are released.

The overnight stay is typically ‘cushioned’ by a collection of egg cartons, on which the moths will doze the night away.

The containers come in 3 common forms – the biscuit tin (a Heath Trap), a small tea crate (a Skinner Trap) and a strong plastic bowl (a Robinson Trap). The lights are normally either blue actinic cold tubes or hot white mercury vapour lamps. The wattage is anything from say 15w on a Heath Trap to 125w on a Robinson Trap. Combinations vary. Robo-traps are acknowledged as having the greatest pulling power, akin to a Porsche 911 in the 1970s. Heath Traps may catch things but are better for storing biscuits.

The trap can be mains powered or a generator for sorties into the field. Here is a recent photo of my Skinner Trap at the Lodge – using 2x 30w actinic tubes. Inside the magic box are 2 perspex sheets, which are sloping downwards to encourage the moths into the lower confines. It is easy to get through the narrow gap between them but more difficult to get out. This trap is plugged into an external socket and left overnight in the garden. They work better in the dark.Skinner Trap-2There are other ways of attracting moths. You can simply hang a light over a white sheet. It can be very effective. Here we see 2 eminent lepidopterists and an enthusiast admiring recent arrivals. Dr. Kendrick is probably drinking San Mig despite the Sprite can. Beer makes moth-ing more convivial –  wine can be used as an alternative. There is no etiquette when it comes to passing the time away. You drink what you can get. The gentleman standing is an internationally renowned lawyer, with whom I have worked several times. The Law is a good way of funding a dangerously expensive moth habit. The middle man runs a hedge fund and is a serious philanthropist. Moth trappingThe problem with moth trapping is that the lights are by definition bright. Curmudgeonly neighbours occasionally whinge about the 125w MV lamps illuminating their nocturnal domain. You can try to position it to reduce the problem and in extremis you can buy black lamps. They of course reduce the catch. My solution was to buy an acre of garden, which is not overlooked. There are cheaper alternatives but why skimp when moths are involved?

I hope this has been useful and if you have any questions (on topic only, please) do leave them in the comments box.

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19 thoughts on “The Moth Trap

  1. My hubby is a lepidopterist. Inactive, but he still retains the knowledge from his teenage exploits. He tells the story of a night when he had the white sheet and the flashlight and a syringe filled with… whatever lepidopterists use to immobilize or otherwise clobber the moths.

    He and his buddy were out in the country. The roads were dark. Dark, that is, until a passing police cruiser took note of the bobbing flashlights and stopped to investigate. The syringe was the focus of the investigation. Hubby somehow managed to avoid arrest. He was rather annoyed, and remains annoyed still to this day, some forty years later. A perfectly good evening was spoiled.

    • We occasionally get approached by the boys in Blue, Maggie but the pros don’t inject them nowadays. They just put a whiff of chloroform or the like into the tube. I don’t kill and pin. Much too squeamish. Nice story though.

  2. Great explanation Andrew. I wonder if a moth trap can be solar generated? Although in the Uk that might be a bit of a problem. Still, if storage of solar energy can be harneshed I am sure a solar moth trap could be a winner. A first on the market and a possible float, Andrew? The hedgefund man and lawyer friend might advice the best way to go forward. 😉

  3. We’re seeing the beginning of our annual month-long moth swarm here in Deep Springs Valley. For the most part I like them, and we see quite a few beautiful sphinx and hummingbird moths. But there are also mobs of rather loathsome medium black ones that I don’t care for so much, and little white ones that get everywhere. And driving at night this time of year can look like accelerating into hyperspace.

  4. I enjoyed reading your explanation. All is very clear now but I actually knew how the moth traps work. Now if you could come up with a method to get a butterfly to stop flitting about so that I don’t need to stress while photographing…

  5. Gosh it has all got a bit more elaborate since my daddy built his moth trap with the aid of and old carton, a light bulb on a flex dangling through a window and four enthusiastic tots.

  6. By far the wisest choice. When the big study at IBSP was done, the beverage of choice was beer in coffee mugs. State land, and all. This has always struck me as a particularly good way to pass a night.
    It is also fun (?) to note all the spider eyes upun one when one carries a torch at eye level.

  7. How are you photographing the ones from the traps, Andrew. I’ve used a sheet in the past and getting a nice stand out is fairly straight forward. But what do you do when they are lazing about in an egg carton? Surely they must put up a bit of a complaint when being removed? I have cooled down a few in the past, but decided I did not want to do that any more, so it’s been either sheets or au naturel.

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