Slug Walk

That would be slowly.... Indeed I can walk frustratingly very slowly and when leading our local Woodland Wanders the participants don't get much exercise.

Via my BSBI membership I was invited on a walk last Saturday afternoon, but not a botanical one, it was to be led by Chris du Feu who is a slug expert, although also well known for writing the BTO Nest Box Guide (23). The site was to be The Field in Dunkeld which is a community owned and run food growing site.

The invitation included bringing some slugs along to be examined, but when I ventured out the evening before, in ideal, warm and wet conditions all that could be found was one Green Cellar Slug, and a Tree Slug, both climbing up the house walls. However, some subsequent investigations, the next morning, under our row of plant pots did reveal a couple of tiny Arion spp, and into a pot they went.

Arion spp are tricky, both large and small, and the hand lens was required to determine these. One turned out to be Arion hortensis which I'd not recorded previously, so that was a bonus. The other was either A. hortensis or A. distinctus but was unclear, demonstrating just how hard to determine these can be.

Arion hortensis.

Chris patiently explained how confusing many of these slugs are and gave us advice on identification, as well as a bit of history as to how they were first found and how they spread across the UK. 

We found a good number of species between us including three Worm Slugs, I'd seen just one of these previously which I found in our Orkney garden. 

Boettgerilla pallens Worm Slug, an almost mythical creature! Certainly my favourite slug. Apparently first found in the UK in 1974, when several were found at one extended site. My Orkney garden record is the most northerly in the UK, just pipping Chris's on Shapinsay.

 The Worm Slug I found on Saturday was a bit of fluke as it got scooped into my sample pot along with organic matter as I caught a Bembidion sp, a ground beetle.

Bembidion lampros, at 3.45mm a small one. Note that the 7th elytral stria is absent. I have seen this previously, but a long time ago.

I did record a few "new for me" species on Saturday, most exciting was the ground beetle Anchomenus dorsalis, of which there were two. This is a very attractive species although my "in the pot" image doesn't show it off to its best.

Anchomenus dorsalis

This is a common species across much of the UK but much less so in this part of Scotland, the dot on the map will be visible!

The other slug which caught the eye on Saturday was Tandonia budapestensis, not one of Chris's favourites! But an interesting beastie nonetheless.

Tandonia budapestensis, Budapest Slug.

I'd never come across the Garlic Snail previously, but one was in the pot of finds. The smell of this species is very, very strong and unmistakable. One of the few species that is best identified by smell and may only be confused with various plants of the Allium genus. Visually this glass snail is very similar to others, and snails are very difficult to identify on the whole.

Garlic Snail Oxychilus alliarius

There were various things found that could not be identified to species including a sawfly larva (but I will investigate that further) and  an Epistrophe sp hoverfly larva (thanks NG).

Sawfly larva (maybe found on Oak), so far undetermined.

Epistrophe sp larva

The female agamic gall formed by the hymenopteran Cynips quercus was found on an Oak.

Cynips quercus f agamic

Several Toads and one Palmate Newt were larger, although not necessarily faster moving, creatures found.

Bufo bufo

Lissotriton helveticus Palmate Newt. I should have checked its throat, but forgot to, over confident perhaps, but I think this is the correct ID.

And I have to finish with a slug really. Deroceras reticulatum is a common species across the UK, although Deroceras invadens appears to be displacing it. D. reticulatum has a "Milk of Magnesia" (a really terrible medicine, I can still recall it as being awful, from my childhood) slime trail, most obvious if you let it move across semi-translucent plastic, like a yoghurt pot.

Deroceras reticulatum

Many thanks to all the participants for a very enjoyable afternoon and especially to Liz for inviting me and Chris for sharing his knowledge and enthusiasm.

Migrants

Moths migrate, and they may travel a very long way. Recently, here in Mid-Perthshire, see previous posts, I've recorded several Rush Veneer and a single Rusty Dot Pearl. On 9th September I trapped a Dark Sword-grass.

Dark Sword-grass

Today, however, whilst talking to the roofers who are currently mending our house a neighbour came across and showed me a photo on her phone. Wow! Convolvulus Hawk-moth. Disturbed whilst moving their lawn. I grabbed the camera and hot-footed it over to their garden where I was just in time to see (and hear, the buzzing of wings) as it took flight and headed off into the distance.

Convolvulus Hawk-moth (Pix IC)

Many thanks to IC for alerting me to this exciting find, I think this is the third record for VC88 (Leverton and Cubitt 2024). Needless to say, despite the less than ideal conditions, clear and cold but becoming cloudy and rainy I have two light traps out tonight.

Birds are also migrating. There have been a few days at home where the hirundines and Meadow Pipits have been clearly on the move. One day I saw nine different Spotted Flycatchers, one group of which may have been a lingering family party but others were likely migrants, also seen recently at home were Whitethroat, and quite a few Willow Warblers and Chiffchaffs. The last Sand Martin (so far) was on 1st September.

We stayed in Melrose for a few days last weekend and there was more obvious vismig there on the northern side of the Eildon Hills. Mostly hirundines but some Mepits, and Siskin also.

Most of the time in Melrose I was looking at plant galls though. There was a small plantation and the oaks Quercus sp were particularly impacted. New for me were Neuroterus numismalis Silk Button Spangle Gall and Andricus foecundatrix caused by the Artichoke Gall Wasp. I'm still working on a few others.

Andricus foecundatrix

Cynips quercusfolii surrounded by Neuroterus quercusbaccarum.

Neuroterus numismalis

There are now some excellent books on plant galls, but also have a look at the website listed in the side panel under Parasites. All the above galls are caused by Hymenoptera.

One evening in Melrose we came face to face with a young Badger, a while since I've seen one of them as they are apparently not present where we stay in Perthshire. 

Following on from dissecting the supposed Svensson's Copper Underwing Amphipyra berbera, the dissection seemed to prove that despite the black palps with obvious white tips, this was Copper Underwing Amphipyra pyramidea. 

Aedaegus with few cornuti would strongly indicate A. pyramidea.

A photo of the underside of the spread hind wing in better, more even light also points to A.pyramidea.

The shape of the uncus, to my eye, is more typical of A. pyramidea, although this is quite a subtle feature.

 A reminder of the palps of this animal.

Amphipyra pyramidea the same animal as the dissection and hind wing above. I think these images prove that the palps feature is variable, as the Evans-Hill paper strongly suggested and not a useful feature for the identification and separation of these two species.

 

I've dissected a few other moths recently as well. Ear moth species are not possible to identify without dissection on the whole, although geography and local landscape can be very helpful. The two I dissected turned out to be pretty typical of their species externally.

Female Amphipoea lucens Large Ear.

 

Close up of the costal process.

Amphipoea oculea Ear Moth, a male. The costal process has two arms of approximately equal length.

My search for Common Rustic Mesapamea secalis in the garden continues to be unrewarded as yet another dissection gave me a male M. didyma. They all seem to be M. didyma in this neck of the woods.

Dissection of a Marbled Minor proved it was indeed that species and a very worn pug turned out as expected to be Juniper Pug Eupithecia pusillata.

Male Juniper Pug Eupithecia pusillata showing the very distinctive aedaegus.

 

Juniper Pug Eupithecia pusillata

Fortunately most moths do not need to be euthanised and examined in such a way, most are identifiable in the field.

The very tiny Acleris forsskaleana

Acleris laterana

Brown-spot Pinion

Common Marbled Carpet

Frosted Orange

Light Emerald

Setaceous Hebrew Character.

The copper underwing problem

Firstly, I will put my hand up to having very little experience of these two species. Just a few caught last year and three so far this year. Last year I caught Copper Underwing Amphipyra pyramidea, once for certain, because I dissected it and then there were another two or three that either escaped or I let go. Once I've proven a species for a site I don't repeatedly take samples. I'm happy to agg. confusion species. At the time I was unaware of the palps feature, which has been given as a way of separating this species from Svennson's Copper Underwing Amphipyra berbera. 

On opening the traps yesterday I found two copper underwings within. Looking at the palps I appeared to have both species. Both moths were comparatively fresh, the A. berbera, especially so. 

Amphipyra berbera lower surface of hind wing. Note how the orange blends across the wing (or perhaps it doesn't enough...).

Svensson's Copper Underwing Amphipyra berbera - or not, this is actually A. pyramidea. Note the very dark palps with pale tips (which have no significance).

There was a bit of a discussion online about copper underwings and it appears that the palps feature is no longer considered good. This seems to be based on a 2022 paper in the Entomologist's Record and Journal of Variation. Whilst I think the overall conclusions of this paper are sound; don't entirely base your identification of either of these two species on one feature - "Many recorders refer to a single characteristic that can be viewed with ease such as the labial palpi or the contrast of the abdominal lateral chequered marking, without reference to any other or to genitalia." My own feeling is that there is a flaw in the argument within this paper because of the samples used for the analysis. Whilst very worn specimens were rejected from the analysis worn individuals were included see below.

 

  (Entomologist's Rec. J. Var. 134 2022). 

 Note with A. berbera the proportion of the sample that were classed as worn.

 What requires further investigation is if an animal that presents with black palps with white tips can it be anything other than A. berbera? (But the animal at the top is A. pyramidea). Surely, these would wear to paler, and thus it would be unwise to use the palps feature to identify A. pyramidea?

What is very useful in the paper is the list of features that are used to differentiate between the two species. What is not mentioned is how difficult some of these features are to use unless viewing from exactly 90 degrees. A number of these features, particular using dorsal views of the fore-wings, require estimation of angles and divergence of lines drawn across the wings. These analyses would have to be carried out from photographs and for them to be features that can be used reliably the photos would have to be taken using accurate management of the angles when they are taken. Whilst this is not impossible with live specimens I would suggest it can be tricky, both these species are quite lively. My photograph above is not suitable for these analyses.

The classic hindwing feature of how the coppery suffusion spreads across the ventral surface of the hindwing is hard to see unless the moth is killed (and even then it's not especially easy), they don't tend to spread their hindwings fully when in a transparent pot. I know some moth trappers are very skilled at managing live moths and seeing these tricky features, but in my experience this is difficult to do, and almost impossible to photograph unless an assistant is to hand.

I took the specimen of the moth above so the hind wing feature is easy to see. Additionally, the discal spot is more typical of A. berbera than A. pyramidea. It will be interesting to see what illumination the dissection brings, but I'm not expecting any surprises.

Here are my photos of the (presumed) Copper Underwing Amphipyra pyramidea. I didn't take the specimen as I have proven this species from the site previously.

 

Presumed Amphipyra pyramidea

What can be used to identify this moth? The palps are worn I would judge and whilst at a glance this would seem to be good for A.pyramidea a cautious approach would suggest not.

Only dorsal features of the fore-wing can be used as nothing else was photographed. Fortunately this photo would seem to be more useful for some analyses as it would appear to be close to a 90 degree view (and I do try to achieve this when I can having the camera set to give me this information when I'm taking the photos). The discal spot is perhaps more typical of A. pyramidea? Feature 10 in the paper does seem to be relatively easy to use  and helpful.

(Entomologist's Rec. J. Var. 134 2022). 

I think that this feature supports an identification as A.pyramidea for this moth. However, a word of caution, whilst A.pyramidea presents this feature consistently A. berbera can be variable so that it may on occasion show these proportions. A further feature referred to in the paper from Clancy 1997 suggests that the alignment of the peaks on the antemedial line and a continuation of that line to dissect (or closely so) the discal spot. Is also a useful feature. This can be seen in Plate 15 above. This criteria may work on the right-hand wing of my moth above, but it is not clear.

On balance I think this moth is Amphipyra pyrimidea.

Why is all this important? The paper gives a good summary of this, basically, the distribution of these two species in the UK is unclear because identification criteria are not used consistently by the various county moth recorders. Additionally, Amphipyra berbera was only recognised as a full species in 1968. In Scotland, whilst the initial colonisations appear to be clear (Leverton and Cubitt 2024), monitoring the future fortunes of these two species relies on consistent and accurate identifications.

 The Les Evans-Hill (2022) paper is available here - https://www.derbyshiremoths.org/wp-content/uploads/2024/08/Guide-to-Copper-Underwings-Les-Evans-Hill-Public.pdf?fbclid=IwY2xjawMigL9leHRuA2FlbQIxMABicmlkETFSWEhXT2VsVHNrMDM3UWJaAR4xv_nHXZS7q2gbrC8o2uYmYJ8HiDeIPzAD58zT0t2Yfxv8eHGJYUJgTVkDgg_aem_e2a-fB-yNYG9321vMVzt3w

A more general post will follow shortly.