Saturday, 14 January 2017

My Highlights of 2016

For me at least, 2016 ended up being rather good for moths even though for much of the year it didn't look as though it would turn out that way.  Well in excess of 900 different species were seen, all of them within VC24 Bucks, and I've chosen ten particular highlights below.  Some of them might seem odd choices but, having produced 16,600 records for the county during the year (many more times that number of individual moths), it was quite difficult to decide which to include and which to leave out!

Netted Pug, Hughenden Valley 26th May
  
Lunar Hornet Moth workings, Westcott
4th May












The first significant find for me was some Lunar Hornet Moth workings in the trunks of sallows which had been felled along the disused railway cutting adjacent to the old airfield here at Westcott.  This is the closest I've managed to get to this species so far - one day perhaps I'll get to see an adult!  Netted Pug has to be one of the smartest of moths and is up there next to Mocha in my list of favourite Bucks species.  Its rare appearances at light traps are definitely something to turn a good session into a great one - I only wish it would turn up more often.

Fox Moths, Stoke Common 6th June
Tawny Shears, College Lake 22nd June













Fox Moth is a very uncommon species in Bucks and to get a pair of females to the same trap at Stoke Common on 6th June was unprecedented for me, especially as two weeks previously I'd been lucky enough to catch another female in Bernwood Forest.  In contrast, Tawny Shears isn't a particularly rare British species but these days in Bucks it is exceedingly difficult to find, so this example caught at College Lake on 22nd June was particularly nice to see.  It was in fact the first occasion that I've ever had the moth to one of my own traps in the county.

Forester, Charndon 28th June
The day-flying priority species Forester exists in Bucks in a number of very small discrete colonies but the discovery of a new location for it happens very rarely, so on 28th June it was very nice indeed to find the species surviving in the corner of some wild-flower meadows at Charndon, some distance north of any other site in the county. 


Triangle, Bernwood Forest 9th July






In our area the rather diminutive Triangle, a Red Data Book macro-moth, seems confined these days to Bernwood Forest although it was once a little more widespread in the county.  It is understood to spend much of its time high up in the tree canopy, making it a very difficult species to see.  The rather windy conditions experienced when trapping in the forest on 9th July may have been the reason why two examples came down to light traps that night.


Sorhagenia rhamniella, Westcott 20th July


It is always pleasing when efforts at providing food-plant in the garden for certain species finally bear fruit!  Alder Buckthorn has been grown here at Westcott for the last six or seven years, originally aimed at helping the Brimstone butterfly, but the appearance of Sorhagenia rhamniella a couple of times in 2016 suggests that it is now being used by other species too.





Dark Spectacle & Spectacle,
Westcott 29th July
Palpita vitrealis, Westcott 3rd September















Quite a few migrant moths were seen during the course of the year, mostly here in the garden.  The beautiful Palpita vitrealis was a first-time visitor to Westcott, unlike Dark Spectacle and for that matter Convolvulus Hawk-moth which I've chosen to leave out, which have both made previous appearances in the garden - not that they were any the less welcome!

The final species was seen during a Bucks Invertebrate Group search for leaf-mines in Bernwood Forest on 15th October.  The active larval case of Coleophora potentillae (below) was found on the underside of a bramble leaf, just a matter of a few hundred metres from where E.G.R.Waters discovered the first for Bucks way back in 1928.  Since then there has been only one other record for the county! 


Coleophora potentillae, Bernwood Forest 15th October

If anyone else has the inclination to present a few notes on some of their own highlights from 2016 during this very quiet period for moths, please feel free!


Dave Wilton
Westcott, Bucks

Friday, 13 January 2017

More detailed comparison of moth trap bulbs



A comparison between two different bulbs using a Robinson trap.

  1. 125W MV
  2. 20W Blacklight “Eco” bulb supplied by Watkins and Doncaster

Throughout  2016 I attempted to find pairs of nights that were not more than a few days apart and with forecast weather conditions in terms of temperature, wind speed and rainfall as similar as possible.  On one of the two nights I would run my Robinson trap with a standard 125W MV bulb and on the other night I ran the same trap in the same place but with a 20W Blacklight (Eco) bulb.


In total 35 pairs of results were obtained.

A summary of the results is given below.

125W MV
20W Eco
Percentage
Total number of moths caught
3078
1832
60
Mean number of moths per night
88
52
 
Mean number of species per night
25
17
68
Total number of different species caught
259
213
82
Number of species not caught with other bulb
83
39
 


 




 


 




 


 




The following table shows in which months each of the pairs of readings were obtained.

1,2
March
3,4,5,6
April
7,8
May
9,10,11,12,13,14
June
15,16,17,18,19,20,21
July
22,23
August
24,25,26,27
September
28,29,30,31
October
32,33
November
34,35
December


Although there were significantly more individual moths and species caught with the MV bulb the differences appeared to be less marked early and late in the season.  I wonder if some of the differences can be attributed to the brighter light from the MV bulb penetrating the surrounding vegetation (particularly deciduous trees and shrubs) in the summer months. It would be interesting to repeat the experiment in a more open situation than where I run my trap.

I have been asked whether there is any indication that the different bulbs attract different species. My feeling is that there was no evidence of this in my results. Of the species caught with only one type of bulb the majority were species caught in small numbers (often only one) and on very few occasions and which bulb attracted them was purely chance.

The few species where there might have been a difference are shown in the table below.  To produce this table I have only chosen species that were caught on 7 or more occasions and then picked the five species that seemed to favour each bulb. My own feeling is that these differences were probably due to chance and a lot more data would be needed to draw any conclusions concerning differences in species caught.

125W MV
125W MV
20W Eco
20W Eco
Both traps
Percentage
Total caught
No. of nights
Total caught
No. of nights
No. of nights
eco/MV
caught
caught
caught
Marbled Beauty
5
3
14
4
7
280
Marbled Green
9
5
16
3
8
178
Common White Wave
4
4
7
5
9
175
Silver-ground Carpet
7
4
11
5
9
157
Hebrew Character
55
8
86
8
16
156
Coronet
33
10
3
2
12
9
Snout
31
12
2
2
14
6
Small Fan-footed Wave
24
5
1
1
6
4
Burnished Brass
13
7
0
0
7
0
Buff-tip
9
7
0
0
7
0


My conclusion from this experiment is that the 20W eco bulb is worth considering as an alternative to the 125W MV bulb especially as the latter become less readily available. It looks as if generally fewer moths and fewer species will be caught on each night the trap is run.

The eco bulb does however have certain advantages.

  1. It uses less than one sixth of the electricity of the 125W MV bulb.
  2. It does not require a choke and is therefore cheaper if starting from scratch.
  3. The light produced is far less likely to disturb neighbours.
  4. I understand that with an inverter it can be run from a battery.


I have no idea of how long the bulb is likely to last or whether it will deteriorate over time.

There are of course other alternatives to MV bulbs but I have no experience of these.


Andy Newbold.  Sibford Ferris, Oxon.