Finding Phyllonorycter ulicicolella and scopariella

In an effort to stave off the winter mothing/butterflying blues that has arguably only led to further suffering, I've spent quite a bit of time over the last few weeks looking for leaf mines on Gorse and Broom. Each plant has a Phyllonorycter species (and broom has a few extra miners of which more later) that makes very subtle mines inside the stems (or leaves/spikes on Gorse) - Phyllonorycter ulicicolella on Gorse, and scopariella on Broom. The unobtrusive nature of these mines, and the fact they're probably easiest to look for during the winter (when most sensible folk are dissecting things and sorting their records for the year) means that they're not recorded very often. In fact, unlike almost all other leafminers in the UK, both species seem to be recorded more often as adults, typically beaten from the foodplant, rather than as mines. Like most leafminers though, they're probably both very under-recorded and waiting to be found at new sites. This has certainly been my experience in the last few weeks. Because lockdown has given me very little else to do, I've now found the mines of ulicicolella at 4 sites, and scopariella at 2. Two of these finds were new for their vice-counties (ulicicolella in VC23 - Oxfordshire, and scopariella in VC5 - South Somerset). All of the sites were new as well, and some of them didn't have loads of the foodplant (and much of it wasn't in great condition), so I'm sure they're lurking out there at lots of new sites, like most leafminers.

In order to justify the hours expended on searching for these two miners, I thought I'd try and put all my photos of them and their habitat together into this blog post in the hope that it also helps others thinking of looking for them develop a bit of a search image by looking at lots of pictures first, before heading out into the field. It should be cautioned that my total count of mines of each species is now about 40 for ulicicolella, and 20ish for scopariella, which is hardly huge, so any generalisations about what kind of plants they like, how variable the mines are etc ought to be taken with a healthy pinch of salt.

What habitat?

I've searched for the mines of ulicicolella at 5 sites now, and found them at 4 of these. The first was Sydlings Copse (Oxon), a very small fragment of rather degraded sandy heath, then Bagley Woods (Oxon, but VC22) not so sandy, just small amounts of gorse growing along the edge of the wood. Next was Greenham Common (Berks) rather stony heathland (acres upon acres of gorse), and finally Willet Hill (Somerset) where small amounts of rather unhappy gorse plants grow along the edges of Sitka spruce plantations, it's stony and rather acid on the soil front here. Phyllonorycter scopariella was then also found at Greenham Common (not loads of Broom here, I searched about 40 plants) and Willet Hill (rather less Broom, a lot of which has been damaged and removed by forestry operations, probably about 20 searchable plants but more being choked in plantations). I think the only take home here is that these sites don't have loads in common geologically or habitat-wise, they just have the foodplants, but in very variable amounts and condition.

Which plants?

With such a small sample of mines (and a not very systematic approach to searching), it's hard to say whether each species has a preference. One thing that it clear is that pretty much all the mines of ulicicolella that I have found have (I think!) been on Western Gorse rather than Common Gorse. Similarly, they seem to prefer the slightly bushier, older growth rather than the young fast-growing stuff (at the tops of bushes, or growing as suckers) that has very large spines. Virtually all the mines I've found have been on the stems of such growth, and not on the spines as some people have found them (I've only found one like this, the first one at Sydlings Copse). This growth seems to be more common on slightly scraggly, older, woody plants (as side shoots off the woody stems), and the highest densities of mines that I've found have been on rather old and unhappy looking plants. Edit: That said, I saw on twitter that it's been found on younger gorse in Gloucestershire recently, and after publishing this blog I saw Jack Oughton's excellent pictures of mines on much younger, thicker growth down in Devon this winter. Edit 2: on 07/03/21 I visited Frilford Heath golf course (in Oxfordshire, but Berkshire for moth recording) where there's a small amount of gorse has been retained, seemingly for an aesthetic finish to the course. I sought out scraggly-looking bushes of the kind where I had found mines before, and checked 3 that I thought looked good. All of them had mines on (8, 7 and 4 respectively).

A rather crude representation of the kind of growth where I've found
most ulicicolella mines.It's not super obvious here, but hopefully
the photos of the actual mines get the point across too.

This gorse bush had 8 mines of Phyllonorycter ulicicolella on - 
Greenham Common (Berkshire)

This very unhappy gorse bush lurking under a willow by the track at Willet Hill (Somerset)
had at least 15 ulicicolella mines on it.

A late addition to this blog after I first wrote it -
this scraggly bush at Frilford Heath
(Berkshire/Oxfordshire) had 8 mines on it.

Another leggy bush from Frilford Heath with 7 mines on

Some wider context  of an ulicicolella site - the small patch
of gorse retained at Frilford Heath golf course. The 6 broom bushes in
the corner of the picture also had mines of Trifurcula immundella.

Having said all that, I'm not sure whether this means ulicicolella has a real preference for these kinds of plants, or they're just much easier to detect on them, when the spikes are small and sparse, and the stems aren't too dense. This is probably why I've found so few mines on the much more densely spiked western gorse. 

As for scopariella, I think the sample is probably too small to say anything really specific. I have found no mines on young suckering broom though, and again, the highest densities have been on slightly larger, older plants. I've found them on some very battered ones too, that have been chopped and damaged by forestry in Somerset.

I found about ten mines of scopariella on this old Broom
being squashed by a spruce plantation at Willet Hill (Somerset)

This rather battered Broom on the edge of a forestry track had two mines of scopariella on - Willet Hill (Somerset)

Two for the price of one: the gorse on the right and the broom on the left here both had their respective Phyllonorycters in residence - Willet Hill (Somerset)

The mines in the field

Phyllonorycter ulicicolella is a very tricky mine to spot, showing just as an area of paler green on the stem, often (but seemingly not always) with some purpley-brown bruising. How strong these features are seems to really vary, and some mines are much more obvious than others. In a couple of instances I've spotted one nice clear mine, and then noticed others next to it while taking pictures.

Two Phyllonorycter ulicicolella mines - Willet Hill (Somerset)

Three ulicicolella mines from the same bush -
Willet Hill (Somerset)

This single very large and obvious ulicicolella mine was on the
same bush as well - Willet Hill (Somerset)

A rather subtle ulicicolella mine - Willet Hill (Somerset)

and a more obvious one on the same bush

I think scopariella is rather easier to pick out, look for an area of uniform discolouration on the broom stem, wrapping round it and continuing up the stem. Initially they seem to be greyish and slightly inflated, before fading to brown and then whitish on very old mines. These old mines are the most obvious, and the ones I've felt happiest recording, as I think some of the greyer specimens of the young mines can look a little like Trifurcula immundella mines (these are basically black, and don't fade to white or anything, unlike scopariella).

Two old scopariella mines at the base of some Broom side-shoots -
Willet Hill (Somerset)

An old scopariella mine on a side-shoot - Willet Hill (Somerset)

The mines up close

There's not much to say about the mines up close that hasn't been stated above, but here are some pictures of them that hopefully demonstrate the features already mentioned, and how they vary.

ulicicolella - Willet Hill (Somerset)

A nice obvious ulicicolella - Bagley Woods (Oxfordshire/Berkshire)

ulicicolella - Greenham Common (Berkshire)

Two ulicicolella mines - Greenham Common (Berkshire)

An ulicicolella mine with strong purple bruising - Greenham Common (Berkshire)

ulicicolella - Greenham Common (Berkshire)

The first ulicicolella mine, and the only one I've found on a spike - 
Sydlings Copse (Oxfordshire)

ulicicolella - Willet Hill (Somerset)

scopariella - Willet Hill (Somerset)

scopariella - Willet Hill (Somerset)

scopariella - Greenham Common (Berkshire)

The same scopariella mine, but from a different angle, showing the 
oldest part of the mine that has faded more - Greenham Common (Berkshire)

Confirming the ID

I don't think I'd want to record either species without opening up a putative mine to check that there is/has been a larva in it (and it's not just some similar-looking damage) by opening it up to look inside. It seems to be okay to record these species without a larva, and just the frass, as nothing else seems to mine in the same way. Opening up the mines so that you can see the contents is tricky for ulicicolella. I initially tried pulling off spikes, and then peeling them back so they stripped away the upper layers of the stem, or using a knife to do the same thing, but I found they removed too much of the stem, often taking the upper layers that contained the larva and any frass. The technique I'm trying now is to 'unzip' the mine rather than peel its top off, by just cutting down the middle of it, either just using a nail or the tip of a sharp knife (I imagine a needle might work as well). This technique seems to work well for scopariella mines too, which are a bit more hollow and split down the middle nicely. Phyllonorycter ulicolella seems to have quite distinctive pale orange-yellow frass that fades to red-brown with age, while the few scopariella mines I've opened up have been quite old and had rather dark frass. 

ulicicolella - the frass is initially quite yellowy as here
(Willet Hill, Somerset)

It gets darker with age though (Sydlings Copse, Oxfordshire)

scopariella - Greenham Common (Berkshire)

scopariella - Willet Hill (Somerset)

I've struggled to find the larvae in the mines, and have only found 5 ulicolella larvae in the mines I've opened up (though I haven't always opened them fully), and no scopariella. The ulicolella larva is quite a weird looking one, being rather long and slim, and was only recently formally described in the entomological literature by Rob Edmunds a few years ago (2005, Ent Rec vol 117, part 4).

Phyllonorycter ulicicolella larva - Willet Hill (Somerset)

A larva in the mine - Frilford Heath Golf Course (Oxfordshire/Berkshire)

Other stuff to look out for

If you're searching over the winter, there are a couple of other things on Broom to keep an eye out for too. Fristly, two miners - Trifurcula immundella and Leucoptera spartifoliella both make linear, blackish mines along the stems. I've only found the former, which can be told from spartifoliella by the distinctive egg case at the end of the mine. I think I may have overlooked spartifoliella, as you still need to open up mines that don't have the egg shell to check the larva (and make sure it's not just an immundella mine on which the egg has fallen off), and I don't normally do this if I've been finding lots of immundella mines (which seem to be quite ubiquitous).

Trifurcula immundella mine, with the distinctive egg in an inset - 
Bagley Woods (Oxfordshire/Berkshire)

There's also an Agonopterix species that feeds over the winter - assimilella, in a spinning between branches, usually obvious thanks to protruding white silk. Again, caution is needed here, as the dreaded Light Brown Apple Moth can also be found in a similar spinning. 

These three species are all described and illustrated in a bit more detail here (along with a nice young scopariella mine), in a handy blog post from Tony Davis. They’re also all featured in Ben Smart’s excellent Micro Moth Field Tips book, and of course, all the miners mentioned here are pictured on Rob Edmunds’ leaf-miner website (to whom a big thanks for confirming the IDs of many of the mines featured here). Later in the year, in spring, there are lots of other things to look out for on Broom, several more Agonopterix species, Anarsia spartiella, Mirificarma mulinella, and the larvae of the Streak can all be found (or not, in the case of the latter on my patch). It's a plant well worth paying close attention to in all seasons.