Species of the Month - March 2019

 Red Sword-grass

Xylena vetusta

The Red Sword-grass is a large and distinctive moth that often comes to lit windows (or moth traps) in March and April, and is also frequent in October and November, hibernating as an adult moth during the cold of winter.  It mates in the spring, and the caterpillars are active, but nocturnal, from May to July, feeding on a variety of plants including heather, bog myrtle, sedges and rushes.  They inhabit damp ground in either wooded or open country.

"The adult can appear as early as the end of August and as late as the following early June, and is thus one of our longest lived moths". (Clancy 2012).  Our earliest is 27 September and our latest is 7 May, so perhaps it doesn't live quite so long in our climate as further south.
 

The Red Sword-grass rests with the wings wrapped around the body.  In this position, the inner part of each wing (on top of the moth) is a deep red brown, and the outer/lower part is a pale straw colour.  This contrast extends for the whole length of the moth, and distinguishes it from the Sword-grass, the only possible confusion species, which could conceivably occur here though we have no records of it.  In the Sword-grass, there is little contrast between the outer and inner parts of the wing, except near the head.
 

The rich red-brown tones seen here in the Red Sword-grass are absent in the Sword-grass which is a much greyer moth.
 

The wings are 24-29 mm long, making it one of the largest moths you are likely to see in early spring.

The colouring of the face and the long narrow rounded body mimic a broken twig, making it hard for predators to spot when resting on a tree or bush.
 

We have two records of the caterpillar.  This one was on heather on Rannoch Moor and was about 49 mm long, on a date of 9 July.  The size of a fully-grown caterpillar is 52-60 mm, and it can be pale green, dark green or black; this one was the pale form. (see ukleps.org)

Our other larval record was on 1 July and not seen by me, but it was reared by Clive Craik and the adult emerged on approx. 19 September.

Please send in your Red Sword-grass sightings using the form below, or email sightings@lnhg.org.uk with the details if you prefer.  If you are not sure of the identity of your moth, please send a photo to sightings@lnhg.org.uk, or put one on the LNHG Facebook page.
 

By filling in this form you agree that the information contained in this form may be collated and disseminated manually or electronically for environmental decision-making, education, research and other public benefit uses in accordance with the LNHG data access policy.  Your email address will not form part of the record and will not be passed on to anyone.

Carl Farmer
LNHG Biological Records Manager

Note you can still send in records for past species of the month.  Here are the previous March species:

Mar 2018 - Reindeer Lichen
Mar 2017 - Butterbur
Mar 2016 - Coltsfoot
Mar 2015 - Hebrew Character
Mar 2014 - Hairy Bittercress
Mar 2013 - Oak Beauty
Mar 2012 - March Moth
Mar 2011 - Frogspawn