2020 so far; LED vs. actinic part 3

When I started mothing almost exactly two years ago, I decided not to use MV lights: I didn't want to buy equipment for which bulbs were no longer made or imported, and I also wanted something that I could run off a battery. I initially bought a 15W actinic strip light (with both mains and 12V DC drivers), but I was interested in LEDs. A year later, having read a lot about LED lights for moth traps, I concluded that those on the market at the time were more-or-less divided into two groups: those that were effective and very expensive, and those that were cheap but not terribly effective. I thought that there was a lot of potential in this area and I wanted to experiment, so starting in late June 2019 I started to design and construct my own LED light. You can read my original post on this here, describing what I built.

At the end of 2019 I made another post (here) with a progress report. As we are now half-way through 2020, I thought I would give a further update. In 2019 I was running a single trap, alternating between LED and actinic lights on different nights. Variations in weather and moon between "actinic" nights and "LED" nights made comparison rather difficult. At the end of the year, I worked out how (i.e. where!) I could run two traps in the garden simultaneously, so I bought another identical trap, spent the first three weeks of January on maintenance and for all of 2020 I have run them in parallel. I have tried to operate the traps twice per week in order to get enough data for comparison, and as there is a difference between the two trapping sites, I alternate the lights between the two locations. During 2020 I have made some other changes, which I'll mention shortly.

The results for these last six months as a whole are below:

2020 H1 Results	Actinic	LED	Overall
Nights run	40	40	40
Species caught	154	166	210
Macro species	101	109	133
Micro species	53	57	77
Best night for species	23-Jun	23-Jun	23-Jun
Species on best night	47	46	73
Best night for moths	23-Jun	15-Jun	23-Jun
Individuals on best night	233	211	392
Total number of moths caught	1136	1449	2585

This makes the lights look similarly effective, with the LED slightly ahead of the actinic. However, this masks the effect of changes I made in April and May, prior to which the LED was slightly behind the actinic. With lockdown, I decided to increase the power of the LEDs, exploiting the availability of mains power in the garden. The LEDs had originally been a total of 14 one-watt components, but in April I replaced them with eighteen 3W LEDs - adding more ultraviolet components. However, the LEDs were not driven at their full 3W rating: I limited the total power to about 18W, compared to the 13W of the original version. The reason for limiting the power is that it is difficult to dissipate the heat; even though I have mounted them on an aluminium heatsink and used thermal paste, they are not tightly bonded and so there is a risk of overheating.

I then found that the UV LEDs were extremely inefficient: this is a common problem at UV wavelengths, but hard to identify because most datasheets do not show the radiation flux (ϕe) that they emit. Only about 2% of the electrical energy was being converted to light and the rest was coming out as heat. After more research, I identified a source of UV LEDs that are about fourteen times as efficient, so in May I replaced six of the LEDs with these better versions. Heat dissipation is still a problem and I am limiting the current so as to keep chip temperatures below a conservative 70°C, meaning that the total power to the LEDs is just under 20W (the drivers consume another 2W).

These changes have made quite a striking impact on the relative performance, best illustrated by the cumulative number of moths caught. Since making the changes, the LED light catches about 35% more moths and 13% more species than the actinic.

7 May 2020 onwards	Actinic	LED	Overall
Nights run	16	16	16
Total species caught…	127	144	182
… of which macros	81	93	112
… of which micros	46	51	70
Total moths caught…	934	1275	2209
… of which macros	605	909	1514
… of which micros	329	366	695

I will continue this experiment for the rest of the year. I may make more changes to the LEDs, but when I think I have finalised the configuration, I will then look to improve the bonding so as to be able to run at a higher power: better bonding generally means it's harder to swap LEDs. I will probably also produce a new set of drivers that will power a subset of the LEDs at a lower current, in order to restore the option for compatibility with running off a battery. Finally, when I am no longer taking the light to bits to change components, I will use a less Heath-Robinson (pun acknowledged) way of mounting the light on the trap, and add baffles - but that might be a job for 2021.

Tim Arnold

Newton Longville, Bucks

Micro id help please

Asking for help again please for id of moths in Jordans!

 I've had a few of these mottled micros last week, here are two of them - ideas?

And this pale veneer type?
Thanks for sharing your expertise!

More Day-flying Moths

A visit to a private site on the edge of Bernwood Forest this afternoon produced Six-belted Clearwing (3) and Narrow-bordered Five-spot Burnet (2).  The clearwings responded to the API lure within seconds at three different spots in what is quite a large site with an abundance of Bird's-foot Trefoil.

Six-belted Clearwing, 29th June

Narrow-bordered Five-spot Burnet, 29th June

In other news, iRecord verification has brought to light two really good moth records for Bucks on 25th June.  One was of a single Forester at Penn Jubilee Wood, yet another new site for the species in the south of the county.  The wood is a recent Chiltern Society planting with wide wild-flower margins in a field just south of the village.  The site was visited again on the 28th when two Foresters were seen and the presence of their food-plant (sorrel) was confirmed.  The other moth seen on the 25th was a Lunar Hornet Moth in Linslade (just inside VC24), the first record of an adult for the county since 2009.

Dave Wilton
Westcott, Bucks 

Phycita roborella ....

..... I think. If anyone could clarify, I'd be grateful. Thanks.

And I have identified this a Grey Dagger, rather than Dark, but appreciate perhaps impossible to say for sure...

Cypress Carpet and some more micros

Some good nights in Merton recently as elsewhere. A Cypress Carpet and Pine Shoot moth are both new for my garden, perhaps arriving with some ornamental conifer planting in the field behind? At least I think it's a Pine Shoot Moth,  too much of a crest for R. pinicolana?
I think the next micros are Homoeosoma sinuella, Acrobasis repandana and Mompha ochraceella looking at some of the recent posts. I am really not sure about the last four.....Any suggestions/confirmations welcome!

Micro query Longwick

I wondered whether this small tortrix might be a Grapholita like Lobarzewski? It is around 6.5mm (W/L) and although not visible in the photograph in some lights has an almost "metallic" sheen?

Advice welcome!

Blackneck in Cookham

New additions to my Cookham garden list have been fairly few and far between recently, particularly macro moths, but finally a new one. A little ragged round the edges, but still a nice Blackneck.

Blackneck - Cookham 26-Jun-20

Steve Trigg, Cookham

Radio

On R4 at 06:35 this morning they repeated Brett Westwood's programme on moths. Still available to listen to on their website if anyone is interested.

Several good nights

As expected, June 24th and 25th were pretty spectacular here in Wolvercote, Oxfordshire, with some species showing up which I hadn't at all expected: notably, Scarce Silver Lines, which I've never seen before, Marbled White Spot (only once before) and Leopard Moth a couple of times.

Leopard Moth, 24/6/20

Marbled White Spot, 25/6/20

Scarce Silver Lines, 25/6/20

Micros were pretty numerous, including some puzzles; I think I have an idea of some of them:

Possible Aleimma loeflingiana, c.9mm, 24/6/20

Possible Parachronistes albiceps, c.5mm, 23/6/20

Possible Ptocheuusa paupella, 24/6/20

But some look fairly distinctive, but haven't yet jumped off the page of the micro bible - if anyone has suggestions, or, indeed, confirmation of those above, I'd be grateful.

Unknown micro, c. 5mm, 24/6/20 

Unknown micro, 24/6/20; possibly a Phycitodes species?

Unknown micro, 24/6/20

Steve Goddard

A Cream-bordered Green Pea and some identification questions

I started to enter the records from Tuesday night into my database and remembered that there were some identifications which I hadn't resolved. The species count of 74 made it another record-breaking night and added twelve more entries to the all-time garden list. The identification of so many unfamiliar moths is very interesting detective work - but also time-consuming! Any help with those below is appreciated.

There were two nice finds amongst the macros: a White Satin (not included in this post) and a Cream-bordered Green Pea. There was also a moth whose identity has completely eluded me - forewing 19mm, and another that looks a bit like a variant of a Short-cloaked Minor (but is probably something else entirely).

Cream-bordered Green Pea

Newton Longville 23rd June

Unidentified

Side view

Short-cloaked Minor??

Amongst the micros, I have provisionally identified Gypsonoma sociana, Lobesia reliquana and Ancylis achatana.

Gypsonoma sociana? Newton Longville 23rd June

Lobesia reliquana? Newton Longville 23rd June

Ancylis achatana? Newton Longville 23 June

Tim Arnold
Newton Longville, Bucks

Yellow-legged Clearwing

Going back in time a little, but still worthy of a mention here is that Ryan Clark found this Yellow-legged Clearwing in Finemere Wood, Bucks on 9th June.  It flew past him while he was looking for beetles - who needs pheromones?!!

IDs and confirmations please

Best catch of the year, hope you can help with the IDs/ confirmations

First a pyrid? I've had a few like this now, I'd assumed they were simply worn but as I've now seen maybe 3 perhaps they just look like that? (sorry about it being in a tube)

I took a shot of the second one "au naturale" but a combination of morning shakes and a new camera meant they were useless so another pot shot.Edit. Here's the shot. Cnephasia?

Edit. Mottled Rustic? This 3rd one has me serously stumped, I've two shots, one lightened considerably to bring out the markings. I thought at first it was one of the minors but they shape is wrong. It seems to have vague blotches and what seems to be a rusty brown streak on the forewing. Underwings are creamy/straw.

Mark Griffiths, Garsington, Oxford.

Leopard Moth and ID question

I was interested to find a Leopard Moth near my actinic light trap yesterday morning, its body longer than its wings. There was another moth on a wall near the trap which I am struggling to identify - second photo below. Could it be a Poplar Grey? Thanks.

John Clough, Marlow

Grass Moth and Acrobasis?

Help appreciated on the following two which I cannot reach a decision over. Thank you.

Steve Lockey (Garsington)

 

Marlow Bottom June 25

A very busy trap last night - mainly flighty geometers and micros, which made processing a bit tricky. I logged 114 species, but probably lost some.

Nothing outstanding, with 68 Riband Wave being by far the most numerous. Having completely defoliated my two small box bushes in the Spring, the first adult Cydalima perspectalis appeared on the 20th, with 7 last night including my first dark form. I wonder how numerous this will be this year.

Of three species of Argyresthia, sorbiella put in a welcome return after one in 2011. Also Acrocercops brongniardella, which is not frequent here. My local population of Recurvaria nanella was out in force with 5 individuals, first appearing on the 20th.

Thiotricha subocellea is also appearing fairly regularly with 2 more last night.

Singles of Silver Y and Plutella xylostella were the only migrants.

Cydalima perspectalis

Argyresthia sorbiella

Acrocercops brongniardella

Recurvaria nanella

Parachronistis albiceps

Thiotricha subocellea

Finally, this slightly worn and perished individual is not immediately obvious to me, c5mm fw - any ideas?

Adam Bassett