Hi everyone
I'm fitting a new funnel lid to my trap and wondered what size of aperture people have on their setup?
As you can see the current funnel is cut to an aperture of 15cm, which I think is too big. Maybe I'm just paranoidly imagining all the Clifden Nonpareil that have escaped during the night before I open it up in the morning! ... Or maybe I'm just jeolous! Anyway the new funnel is only 3cm which feels to small.
So big enough to catch to a Privet Hawkmoth by small enough to keep most things in; what do you think?
Andrew Cornick SU28
Hi there. Mine is the standard (at least in 2005) Watkins & Doncaster bulbholder which has a diameter of just over 11cm and is divided into four open segments by cross-bars. Clifden Nonpareils seem to like it. But I think the lobster pot effect of almost any funnel may keep moths in. Good luck!
ReplyDeleteI have a homemade set-up with an old cooking funnel that I cut to size. I used to have quite a small aperture of around 5cm but this year I increased it to around 10 or 11 cm with a noticeable improvement in results.
ReplyDeleteHi Andrew
ReplyDeleteYes I would say your current setup has too wide an aperture and you will be losing quite a lot, not just big things, especially as your funnel looks shallower than the standard (although I could be wrong).
As Martin says, the standard Robinson-pattern trap funnel is 11 cm in diameter at the narrow end. However, each of the four actual apertures is only 3 cm in diameter with a max. length of about 4.5 cm. I will send you a photo.
The base appears to be a W&D one so I suggest you cut the funnel to 11 cm but fit another bar at 90 degrees, which would also give the bulb fitting greater stability. I have used Robinson traps for over 45 years and have always been amazed how things like large hawk-moths get in, but get in they do. I am also sure a Robinson retains the catch better than any other design.
Can I also ask - the egg trays in the photo are very close to the apaerture. Are they in that position when the trap is operational? If so they are far too close to the aperture. I have 12 egg-trays in each trap, cut in half. I lay 3 around the bottom, then 3 more layers of 3 at a low angle, alternating so there are spaces for large moths and those that like to go under something to hang underneath. I had 4 Robinson traps running at a site in Kent this week, and a huge female Clifden Nonpareil was underneath just such a space on the very first egg tray I picked up. This arrangement should help settle the moths and result in them damaging themselves less.
Actinics - the older traps had an aperture of about 7.5 cm but those on sale these days have about 6 cm, which I regard as too small so I cut them to 7 cm. It may depend to some extent on the overall design of the trap and the thickness of the baffles, but I reckon 7 cm is about right. I have had a Clifden Nonpareil inside a Heath with 6 cm aperture, but it can't have been easy! It is very difficult to compare results of light traps with slightly different designs across years.
Hope this helps
Martin
Thank you all so much for the helpful and considered replies. My weekend task is to come up with a new funnel arrangement. Thanks for the thoughts on egg trays Martin. The ones in the photo are just thrown in after the last trap, but when in use I do have them stacked up higher than four layers, so I will try your arrangement as well.
ReplyDelete