2019 review, LED vs. actinic pt. 2

A week ago, Dave posted his annual review of what he had caught in his garden. I'm just finalising my records before sending them in, so I thought I would do something similar. Since early July, I've been alternating the light I've used between a 15W actinic strip and a 13W LED light that I designed and constructed myself, so I have also broken down the figures by the type of light I've used. I've carried out a similar analysis to Dave, apart from the additional breakdown between actinic and LED light and the absence of a comparison with previous years because this is my first full year of mothing. Here are the results for the year, with apologies for some small formatting issues that aren't in my Excel originals, but which appear when I paste the tables into Blogger:

2019 Results	Actinic	LED	Total
Nights run	25	13	38
Of which nights run before July	12	0
Species caught	143	117	182
Macro species	102	82	127
Micro species	41	35	55
Best night for species	25-Aug	27-Aug
Species on best night	47	59
Best night for moths	25-Aug	10-Jul
Individuals on best night	351	594
Total number of moths caught	1569	1831	3400

Highest total counts for a species	Actinic	LED
Macros	135	302
	Heart & Dart	Square-spot Rustic
Micros	97	427
	Agriphila geniculea	Chrysoteuchia culmella

The figures above only cover moths caught at home, in the trap. They exclude 43 moths found indoors, attracted to a lighted window, etc. The figures also exclude other sites. The total number of species caught is less than the figures for LED and Actinic light added together, because many species have been caught by both lights.

As I only started to use an LED light in July, I performed a separate analysis of the second half of the year, when I've been alternating the two kinds of light - in a previous post, I mentioned that I don't run the two lights on the same night, and on many occasions weather conditions & lunar phase haven't been comparable from night to night. However, it's probably OK to compare them in aggregate. Here are the figures starting from July, when I began alternating the two light sources:

July 2019 onwards	Actinic	LED	Total
Nights run	13	13	26
Total species caught…	120	117	162
… of which macros	81	82	108
… of which micros	39	35	54
Total moths caught…	1238	1831	3069
… of which macros	928	1153	2081
… of which micros	310	678	988

I had a feeling that although they seem to be catching similar numbers of species, they might not be catching the same species. In fact, this is quite striking: of the 108 species of macro moth caught since July, only half of them (55 spp.) were caught by both lights: the actinic got 26 species that the LED didn't, and there were 27 moths caught by the LED and not by the actinic.  For micros, the figures are even more striking: 54 spp. overall, 20 by both lights, 19 actinic-only, 15 LED-only.

So I deepened the analysis to see if there was a pattern. I'm still working on this, but it would appear that there is no pattern related to families or to sub-families.  As an example, the actinic "missed" three species of Ennominae that the LED caught (including Canary-shouldered Thorn and Willow Beauty), but the LED "missed" five species in that same sub-family which the actinic caught (including Dusky Thorn and Mottled Beauty). Flight periods shouldn't be much of a factor, since I nearly always manage to run the trap with the two different lights within a week of each other.

What do I conclude? There's not much difference between the two lights, at least in terms of the numbers of species caught. I'll continue this next year to see if any pattern emerges about which light is better with specific species, but I suspect that this could be fairly random.  The LED did catch more individual moths, although in the case of the micros, this is largely down to one night with a huge number of Chrysoteuchia culmella coming in from the field 3 metres away.

Tim Arnold
Newton Longville, Bucks