Grass ID guide needed

John Langmaid joined me for some fieldwork on Wednesday so, inevitably, having a grown-up present, I saw a couple of species I've not seen in the larval stage before. Spring is the best time to look for most Elachista species as larvae and as most of them rarely seem to come to light, this is the best way to record them.

The down side is that most Elachistas mine grasses, sedges or rushes! So, get your grasses book out or hire a tame botanist and have a look for:

This is Elachista humilis and the larval foodplant is Tufted Hair-grass Deschampsia cespitosa.

The Nationally Scarce Elachista obliquella produces a simlar mine on False Brome Brachypodium sylvaticum although the leaf is somewhat more twisted by the mine.

Nemapogon clematella

The larvae of Nemapogon clematella feed in fungus on a variety of trees and shrubs and can be detected by frass exuded from the fungus. This seems to be particularly easy to find on the small black fungus that occurs commonly on dead Hazel stems in overstood coppice. The moth can be bred easily.

Norway Spruce

So why have I got a bag of Norway Spruce cones in my house? Well it isn't to spray them for christmas decorations!

The larvae of two species can be bred from Norway Spruce cones collected at this time of year; Assara terebrella and Cydia strobilella. Cones containing A. terebrella larvae are reported to be stunted and sometimes deformed but those with C. strobilella rarely show any external signs of being occupied so you just need to collect a random selection. Whilst A. terebrella comes to light, people don't often trap conifer plantations so it is under recorded. C. strobilella flies around the top of spruces in afternoon sunshine and is therefore rarely recorded as an adult.

Cones that are collected now should be kept in a container that allows circulation of air (to prevent mould) but you will obviously need to have some sort of netting over the container to prevent any emerging adults from disappearing before you notice them! I give the cones a light spray with water occasionally.

Broom - adding to the confusion

I found some more mines on Broom over the weekend and, wanting to try to get a decent photo of the mine of Trifurcula immundella or Leucoptera spartifoliella, I brought one back. It's a difficult mine to photograph but you should be able to see that it starts on the uppermost right hand branch, goes down the right hand side of the main stem before moving to the front of the stem by the middle right hand branch then turning by the lower left branch to start travelling back up again. This mining down then up method is referred to immundella in some of the literature but there was no sign of an egg, even under the microscope, which means it should be spartifoliella. I decided to open the mine to make sure and the larva is clearly immundella. I would recommend that if you can't see an egg, you open the mine and have a look at the larva to confirm which species it is.

Moths on Broom in winter

There are a few things that can be looked for on Broom at this time of year (and it's much easier when there are no leaves in the way!). They range from the very common and easy to find, to the somewhat more difficult but if you know somewhere with a few bushes you should be able to find at least one species.

Agonopterix assimilella larvae seem to be everywhere I look. They spin a couple of twigs together as shown below (although the silk may not be quite as obvious as in this example).

It is important that you gently pull the twigs apart until you can see the larva and check that it looks like the photo below. This is because the dreaded Light Brown Apple Moth has been recorded on Broom and makes a similar spinning. No doubt there will be other polyphagous species that also do something similar.

The other three species are all miners. In all cases they mine the most recent years growth so the mines will be found relatively near the end of the twigs. The mines of Leucoptera spartifoliella and Trifurcula immundella are, in my opinion, inseparable. Some literature states that one species mines up the twig and then back down, whilst the other mines down the twig and then back up. However in my experience this is not reliable. My pictures of the mines are not great, nor are those I can find on the web but both mines are blackish as can be seen in the photo below.

The way to separate the species is that the egg of T. immundella stays fixed on the twig at the base of the mine, whilst that of L. spartifoliella falls off soon after the larva hatches. The photo shows the egg of immundella at the start of the mine.

If you want confirmation, you can carefully dissect the mine and look at the larvae which are very different:

The larva of T. immundella is shown above and that of L. spartifoliella below.

The final species, and perhaps the hardest to find, is Phyllonorycter scopariella. The mine is shorter than the two preceeding species and tends to be greyer or browner. The books say that the mine is 'inflated' and this is true if you use your imagination a bit!

Pond dipping

Whilst looking for a rare Coleophora in Norfolk on New Years Day I noticed some reedmace with damage to the seedheads (see below).

This rang a vague bell about 898 Limnaecia phragmitella so I picked a seedhead to have a look for larvae. I expected the larvae to be hidden within the seedhead but they were feeding on the outside. This species will feed on both Common and Lesser Reedmace.

Finishing off Holm Oak

Below are upper and underside views of the blotch mine caused by Phyllonorycter messaniella on Holm Oak. At this time of year the underside 'skin' of the leaf mine is often torn but it should still be recognisable.
If the mine is intact, note the crease which is a feature of many Phyllonorycter mines.