Wednesday, 22 August 2012

Heath-Robinson Moth Trap

When Badger took back his moth trap my VLW was rather relieved: perhaps this new low in my nerdiness was just a temporary blip. But I found that I was missing the mothing: setting it all up in the evening and watching it to see if there were any early arrivals, all the excitement of wondering what was in the trap each morning, it was rather addictive! However, I knew that getting my VLW to authorise a top of the range Robinson trap that came it at over three hundred quid was going to be somewhat problematic so I thought that I'd have a go at building my own. Now, I'm not know for my handywork - I've always been more of a theoretician rather than a hands-on sort of chap but I did some research and came up with a very cost-effective moth trap. Here's how I did it.

The most import aspect is of course the light and the electrics I wasn't going to bother trying to cut corners here. From experience with Badgers MV (Mercury Vapour) light, I decided that it was just too bright for a suburban setting and also got rather hot so one worried about running it if it were to rain. I therefore decided to go for an Actinic bulb instead which puts out mostly UV light so is not nearly so blinding and also runs cold so won't shatter in the rain. I'd read good things about a supplier called Paul Batty in Sheffield so looked him up. He has about the worst web-site I've ever seen but he does sell what you want and was happy to discuss my requirements over the phone. I ended up buying a 40W Actinic U-shaped bulb + electrics from him, some vanes in which to mount them and an 18cm plastic funnel for the grand total of a little over £70. The next stop was Ikea where I picked up a plastic storage box for a couple of quid. I cut a hole in the lid - this was rather difficult because the plastic was rather prone to split so I drilled some holes in it first and then used some garden secateurs to cut between them. The lid goes on the box, the (sawn-off) funnel goes in the hole and the vanes and light rests in the funnel. I added some dark black sheeting (the stuff you lay under gravel to stop weeds coming through) over the lid to ensure that it's nice and dark inside for them to rest (the lid is somewhat transparent) - this can be lifted off to see what's inside when required. I sourced some large egg box trays on eBay for £1.50 + postage and voilá a "Heath-Robinson" moth trap for under £80.

My "Heath-Robinson" trap. Note the black weed-control cover - 
I often find moths tucked away in there rather than in the trap

So how well does it work? Well, the truth is an Actinic bulb doesn't attract quite as many moths as an MV one but I still get plenty coming in. I'm still experimenting with details such as the hole size at the bottom of the funnel and whether a bigger box means fewer escaping moths. When I set it up in the evening I've been checking up on it for the first hour or so to see how it works. It's effectiveness seems to vary from species to species: Brimstones seem to love the Actinic light and I get loads of them fluttering about though they don't seem to go near the funnel at all and I don't often get one in the box. Large Yellow Underwings on the other hand head straight for it and straight down the hole with a satisfying thud! By patrolling the trap for the first hour I've managed to get sightings of all sorts of extra moths that never otherwise make it to the trap. I also find that come the morning it's worth looking carefully around the area, including on the shed wall and on the bags and flower pots nearby for sheltering moths. Some of my "best" moths have been found like this.

In terms of numbers, it's a sad fact that being in an urban environment means that you're going to get fewer moths that out in the countryside. My best count to date is probably 50 moths in and around the trap whereas I know that Ewan Urquhart gets far more than this number every time. Still at present this is more than enough for me and it usually takes quite a while just to work out what they all are. For identification, when I'm clueless or would just like confirmation I turn to the internet. I've more or less given up on iSpot now and just use the BirdForum Butterfly and Moth ID sub-forum which is really great. There are a group of us who regularly post their ID queries there and several experts who can pretty quickly come up with the ID's. I've even started suggesting ID's myself now on some of the easier ones and so far no howlers by me!

One side benefit of not having so many moths coming to the garden is that I've started looking at the micro's as well. These are really tricky little blighters but fortunately the BirdForum experts are pretty hot on these as well. I've managed to add one micro (Agriphila Geniculea) to the Upper Thames Valley Moth Year List so far which was rewarding and I've compiled a photo library of all the garden micros that I've caught so that I can check up there first before asking on-line.

The fact that I'm enjoying this so much has lead me to ask what aspect of it exactly is it that's appealing (my VLW asks this regularly as well!). There seem to be several components: 

1) Learning to identify things. This involves acquiring the experience and ID skills to be able to identify different species. For the same reason that I like trying to ID tricky gulls I also like getting to grips with tricky moths.

2). Collecting things: the satisfaction of ticking things off a list. I know for a fact that I'm a very list motivated person and in my everyday life I like to work through lists of things that I need to do so it suits my personality. I've even made this list of why I like mothing!

3). The unpredictability and excitement of wondering what you're going to find in the trap each morning.

4). Dealing with nature in all its amazing forms and variation. You realise that there's another whole nocturnal world out there which I'd had no idea about.

These aspects apply also to birding of course and I'm sure that most readers of this blog will relate to most of the points above.

Anyway, enough of the waffle, let's have some good old moth porn to finish off. Here's a selection of some of the highlighs of my recent catches.

Copper Underwing -it's hard to distringuish this from Svennson's CU -

 Large Yellow Underwing - my comonest macro moth at the moment, I'm getting loads of them
 Red Underwing - found on the shed by the trap the next morning
 Setaceous Hebrew Character
 Marbled Beauty
 Old Lady - a huge beast
 Knot Grass
 Double-striped Pug - most Pugs are rather boring but this is quite a looker
Flounced Rustic

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