Wednesday, 7 March 2018

Sawflies to look for in March

After a long winter, and especially after a snowed-in first week of March, I’m looking forward to some warmth. As it’ll be my first spring as county sawfly recorder, I thought I ought to work out which are the first species we should be on the look-out for. So I’ve spent a couple of evenings going through 'Benson' and 'Quinlan & Gauld' {note to self - I’ll need to do a blog post soon on the identification literature}, and tabulating the flight-period information contained therein. That is, in the identification keys where you get to a species, it gives details of range, status, larval food-plants and flight-period, e.g. under Cladius pectinicornis Benson gives ‘V-IX’ (i.e. May to September). It’s half a century out of date, likely to be affected by climate change, range spread and taxonomic revisions (I may well be missing some post-Benson spring species from this article), but it’s the best I’ve got access to. You have to start somewhere.

So, what did I discover? Firstly, no species was listed as being on the wing in January, so that’s good – we didn’t miss anything there. There is one species – Dolerus anthracinus - listed for February, then 14 in March. After that the monthly totals rise sharply, peaking in May and June, before dropping away again quite quickly. Sawflies do seem to be a group that feature most strongly – in their adult form at least – in late spring and early summer.

Rough number of adult sawfly species on wing each month

What to look out for in March then? The 14 species I noted were as follows:

Family Tenthredinidae
[Subfamily Nematinae]

Amauronematus histrio – locally common throughout Britain and Ireland on Willows Salix (incl. cinerea, alba, fragilis). Appears to be unrecorded from Norfolk to date.

Amauronematus leucolenus – locally common in S England, also on willows Salix (incl. cinerea, aurita, repens). Appears to be unrecorded from Norfolk to date.

Amauronematus tunicatus – local in England and Ireland from willows Salix (incl. cinerea, aurita). Appears to be unrecorded from Norfolk to date.

Amauronematus viduatus – another willow Salix species (incl. repens, cinerea, aurita, caprea), locally common throughout Britain and Ireland. We have a previous record from West Harling in March 1990. Included in county checklists by both Bloomfield (1909) and Durrant (2000).

Pristiphora glauca – Benson listed six English and Welsh counties, including Norfolk, with the larval plant listed as larch Larix. Not on any of our county checklists though, so unclear if the latter overlooked the record Benson was referring to, or whether they re-assessed it and found it unverifiable.

Pristiphora pseudocoactula – a rare species in Benson’s time, with records only in Devon, Surrey and Herts. The larvae occur on birch Betula. Not on the Norfolk list.

[Subfamily Selandriinae]

Dolerus madidus – local throughout Britain & Ireland, larvae feeding on rushes Juncus. Bloomfield (1909) listed in his county checklist but Durrant (2000) omitted, so not sure of Norfolk status and perhaps need to look at specimens held in the museum? Featured on Naturespot.

Dolerus anthracinus – larvae on grasses, locally common throughout Britain ("in SE England mainly on chalk grassland"). An old record of this species exists from Wheatfen in 1940. Bridgman (1888) listed for Eaton but Bloomfield (1909) omitted the species, so perhaps had some doubts?

Dolerus coracinus – only known from Aviemore by Benson, larvae unknown.

Dolerus haematodes – widely distributed, larvae on sedges Cyperaceae and grasses Poaceae. Included on county checklists by Bridgman (1888), Bloomfield (1909) and Durrant (2000) but no more recent records yet. Featured on Naturespot.

Dolerus nitens – widespread but rare, larvae presumed on sedges Cyperaceae or grasses Poaceae but undescribed (in Benson’s time at least). Bloomfield (1909) includes on his county checklist but not listed by Durrant (2000). No more recent records. Featured on Naturespot.

[Subfamily Tenthredininae]

Aglaostigma aucupariae - larvae on bedstraws Galium (incl. mollugo,boreale). Very common throughout. We have several records of this species in the county database, including one I found on 26th March 2017 at Caistor St Edmunds Roman fort. Featured on NatureSpot. Important to note there is a similar species A. fulvipes which emerges slightly later, but might well be in a warm March (try to get photos of the side of the abdomen as well as from above).

Family Xyelidae

Xyela julii - a very small species, less than 5mm long. The larvae are in staminate cones of Scots Pine Pinus sylvestris but the adults feed on flowers of other nearby trees, especially birch Betula. Locally common, even abundant, on heaths and widespread in Britain & Ireland. We have a record in the database from West Harling in 1991, and included in county checklists by Bridgman (1888), Bloomfield (1909), Atmore (1914) and Durrant (2000). Featured by Steve Falk who suggests the common name of 'Fairy Sawfly'.

Xyela longula - also occurs on Scots Pine Pinus sylvestris but apparently only recorded in Aviemore.

So, in a Norfolk context, it looks like we should be hunting for 11 species of adult sawflies in March around willows (4 species of Amauronematus), birches (especially on heaths near pines for Xyela), larches (Pristiphora), bedstraws (Aglaostigma) and rushes/sedges/grasses (4 species of Dolerus). That’s enough to be going on with - I wonder if we can find any of them? Let me know if you do.

To reiterate, this is a brief guide to inspire a bit of hunting. If you find something, it won’t necessarily be one of these listed species, but they’d seem like a good place to start. However, please try to get a series of good photos from multiple angles if you can, or even more usefully, get keep a specimen (I suspect this might be particularly important for the Amauronematus and Pristiphora - oh and yes Dolerus too. Basically, most of them!)

1 comment:

  1. Hi Andy, I recorded Dolerus nitens at Barney Wood last March, but haven't put it on iRecord yet as I thought you'd want to check the specimen.