Thursday, 1 September 2016

Westcott, Bucks

Last night's collection of moths in the garden (241 individuals of 53 species) was fairly typical of recent catches.  New species for the year continue to appear here although not at a rate which is going to break any records.  I've now just struggled past 500 for the year which, going on previous form, means that the final garden total for 2016 will be something like 560 or 570.  Unlike the previous two seasons, 600+ won't be achieved this year.

(25th August)  Gold Spot
(26th August)  Aethes smeathmanniana, Centre-barred Sallow
(27th August)  Cacoecimorpha pronubana, Scoparia subfusca, Sallow, Red Underwing
(28th August)  Agriphila latistria
(29th August)  - nil -
(30th August)  Lobesia abscisana, Vestal, Feathered Gothic, White-point
(31st August)  - nil -

Agriphila latistria, Westcott 28th August

Feathered Gothic, Westcott 30th August

Vestal, Westcott, 30th August

The Red Underwing is one of my latest dates ever for a first sighting here as it usually appears in early August (sometimes even late July) thanks probably to the enormous willow in our front garden.  Agriphila latistria is new for the garden and indeed for VC24, Bucks being the last English county south of Yorkshire requiring a record of this easily-overlooked grass moth species.  Keep checking those tristellas!

The garden finally got its own Vestal record for 2016 on the 30th.  As Steve Trigg mentioned in an earlier post, they usually end up on vegetation close to the light, as was the case here (thinking about it, I don't think I've ever had a Vestal inside a trap).  This underlines the importance not only of checking the periphery very carefully but also of getting up early enough to beat the birds.  My alarm is currently set for 4.45am and that gives a reasonable half-hour window before one of our garden Robins starts "tutting" away, getting very annoyed that I'm keeping him from his breakfast.  It also means that I often beat the wasps which usually start flying around this time and can be quite a nuisance at this time of year.  I find that sometimes 20% of the nightly moth catch can be outside the trap, on the grass or adjacent vegetation so it is always worth getting up early or else risk losing something important which hasn't already been snatched by a bat!

There have been lots of other nice migrants around lately but this far inland we have to be very lucky to catch any of them.  Silver Y has, of course, been doing quite well and Udea ferrugalis and Nomophila noctuella continue to appear here almost every night, as they have for much of August (six ferrugalis on the 30th was a record here, last night it was just one of each which is more usual).  However, notable by its absence so far this year has been Dark Sword-grass which I get annually without fail.  Still, there's plenty of time yet...

Numbers of Brimstone now seem to be in decline, having reached a peak of 48 here on both 23rd and 25th August.  Dusky Thorn is also winding down after a good season (148 recorded in the garden up to 31st August).     Flame Shoulder, Large Yellow Underwing, Small Square-spot, Setaceous Hebrew Character and Square-spot Rustic are now providing the highest totals each night.  I had a fresh Clouded Silver on 30th August which must surely be an attempt at a second brood.

Two of the most interesting visitors to the garden trap over the past week have actually not been moths, the first being the long-horn beetle Arhopalus rusticus (25th) and the second being the enormous and mean-looking ichneumon wasp Stauropoctonus bombycivorus (27th).

Dave Wilton
Westcott, Bucks


  1. Dave,
    First thanks for your continued updates which on the whole mirror my own
    but of course to a much lesser degree. But my main query is regarding the frequency of trapping. When I, a few years ago, took up this fascinating pursuit I, of course, did a bit of homework. One thing I do remember from one of the help sites was the recommendation that trapping on too many successive nights could affect breeding and should be avoided.
    What are your thoughts on this?,

  2. I don't think there is much evidence of this at all Steve, so I wouldn't worry too much. Moth traps don't draw in all the moths in the area each night, just a sample.

    Dave, I'd love to get up at dawn each morning, but I can't do it, so I check around the trap at midnight, or thereabouts to see what is around. Not perfect, but horses for courses.

  3. I agree with Peter. Our village back garden is a reasonable size though not enormous but it is surrounded by fairly dense hedging of assorted native trees and shrubs, so when the trap is on very little light escapes from it other than straight up. The trap could perhaps be said to be a disturbance to breeding purely within the garden when run every night but I haven't noticed it and I still stumble across the more obvious larvae of things like Vapourer, Yellow-tail, the Daggers and many leaf-miners quite regularly. It might be different if everyone in the village ran a garden trap every night but at the moment I'm fairly sure I'm the only one out of circa 130 houses. Something else I'm quite religious about is releasing the catch away from the garden to minimise re-catches - I have several spots to choose from a mile or two away locally which I drive to in order to release the catch. The individual moths are therefore only inconvenienced for one night.

    As to getting up early - I do go back to bed again! Once the trap is safely in our cool window-less garage with the light on the moths quickly settle down for the rest of the day. I quite often don't get around to processing the catch until the afternoon. The way I go about things won't suit everyone but it might offer some ideas. Exactly, horses for courses.

  4. Many thanks for your responses. Like all things in life there are always different opinions. I shall try to get up earlier and be less of a slugabed!.

  5. My 2 pence worth as I have people continuously questioning my ethics as I also run my trap nightly:
    1. 7-8 years ago in Oxford garden I did an experiment to look at recapture rates using common species, mainly Heart and Dart. Back then I would catch over a hundred a night during peak flight season trapping in same location in garden every night and unlike Dave released all moths back in garden: in this experiment released them next to trap site. I marked all Heart and Dart and a few other species that I caught every night for a couple of weeks during the peak flight period. I don't have the exact stats to hand but I regularly caught between 30 and 100+ Heart and dart each night over that period and never re-caught more than 5 or 6 individuals and repeated capture of the same individuals over that period was extremely limited. Some of the other more sedentary species I marked were recaptured more often but what I proved to myself is that most moths are fairly mobile with high turnover. In many mark-recapture studies recapture rates tend to be around the 5% level - i.e pretty low. This isn't limited to moths - studies on birds have showed that the familiar garden robins, blackbirds and blue tits that are often assumed to be the same individuals as they’re seen every day, are often many different individuals outside the breeding season.
    2. Although some of the light used are not as attractive many people have their house lights and security lights on all the time and street lights etc are on all night every night in most places. Compared to the relatively few moth-ers who trap nightly these must have a much, much greater impact and no-one collects any information from the moths at these lights so they provide no data on distribution, abundance etc unlike the data collected from moth trap lights.
    3. the greater proportion of moths attracted to lights tend to be male. You could argue that this could be attracting the males away and reducing mating but most female moths you do capture at light traps tend to be fertile (readily lay viable fertilised eggs) which means they have been successfully mated already - at least in my own experiences.
    4. studies on street lighting are showing some negative impacts on moths and other animals, potentially disrupting pollination services for example. But, further and many more studies are required to look at the myriad of potential impacts (increased predation, drawing moths to unsuitable habitats, disrupting reproduction and oviposition etc) and the consequences on moth populations. A major issue is the most effective way of capturing moths and thus acquiring sufficient data is by light trapping!!
    In conclusion, for me personally I do feel that there are likely to be some negative impacts, but also there are positive gains from continuous trapping, such as getting good data on species phenology and how this is being affected by warming climate etc, how abundances change throughout the season, local migration, increased ecological information (for example showing the different generations of multivoltine species and how this varies from year to year and across a species' geographical range). And the negative impacts of moth trapping are minor in comparison to the major impacts such as habitat destruction, degradation, cars (windscreens), pesticides, herbicides, keeping gardens neat and tidy etc etc. The positive knowledge and data we acquire to help get a better understanding of moth populations, in my opinion, must outweigh these small negative impacts. One thing that is crucial though is that data collected from moth trapping is submitted otherwise there isn't that positive impact!


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