Northern Ireland's Priority Species

Diarsia rubi – small square-spot

Diarsia rubi

Diarsia rubi (Vieweg, 1790)
Family: Noctuidae

This is a widespread and common moth, found throughout Northern Ireland. It could be described as the archetypal dull brown moth! It has few obvious distinguishing features to the uninitiated. It can be found in a wide variety of habitats including suburban gardens. There is no evidence of decline in Northern Ireland but in the UK it has declined by 74% over a 25 year period.

In brief

  • Very common species found in a wide variety of habitats but especially damp woods and pastures
  • It has two generations in Northern Ireland, May-June and August-September
  • It is frequently attracted to light
  • A Northern Ireland Priority Species because of declines detected in other parts of the UK where it has undergone a 74% decline over a 25 year period. There is no strong evidence that the species has exhibited a similar decline in Northern Ireland but as we are part of the UK it has been included on the Priority List

Species description
A medium-sized member of the Noctuidae, very typical of the family, with wings folded over the body. The base colour is brown which is banded with darker or reddish brown. A small neat black dot on the forewing is a good aid to identification.

Life cycle
Two generations, May-June and |August-September but individuals often occur between these times. Over-winters as a caterpillar. Pupation takes place below ground. The caterpillars feed on a wide variety of herbaceous plants including dandelions and docks as well as heather.

Similar species
There are a number of similar species but the most similar are the Ingrailed Clay and the Square-spot Rustic. The latter lacks the neat black dot between the orbicular stigma and trailing edge of the forewing. The former can be very similar and is best separated by the stronger marbling on the forewing.

How to see this species
Flies from dusk and comes to light and sugar. It can often be found feeding on ragwort flowers. The species can be encountered just about anywhere in Northern Ireland.

Current status
Common and widespread, occasionally trapped in significant numbers.

Why is this species a priority in Northern Ireland?

  • Listed as a UK Priority Species and therefore on the Northern Ireland Priority List by default
  • Rapid decline (74% over 25 years 1968-2002) assessed using Rothamstead trap data

Threats/Causes of decline
It is thought to be declining in the UK as a result of many factors, including habitat change, pollution and the use of pesticides.

Conservation of this species

Current action
In Northern Ireland there are no specific actions proposed for this species.

  • Occurs on many designated sites

Proposed objectives/actions

  • Increase Rothamstead Trap network to gather data on status
  • Encourage submission of records to the Moth recorder

What you can do

  • Report all moth sightings to the Moth Recorder for Northern Ireland, Andrew Crory, or use the Butterfly Conservation Northern Ireland (BCNI) sightings web page at The BCNI database is managed by CEDaR and these records will then be used to update the Butterflies and Moths of Northern Ireland website.
  • Join Butterfly Conservation. Butterflies and Moths are in serious decline — with your support Butterfly Conservation can take action to reverse this.

Further information

The Butterflies and Moths of Northern Ireland

MothsIreland Website

The state of Britain's moths - an explanation as to how declines have been calculated

Background information on the Rothamstead Trap Surveys

UK Moths Website with an up-to-date distribution map

Porter, J. (1997). The colour identification guide to caterpillars of the British Isles. Viking, London.
Skinner, B. (2009). 3rd revised and updated edition. The colour identification guide to the moths of the British Isles. Apollo Books.
Thompson, R. & Nelson, B. (2006). The Butterflies and Moths of Northern Ireland. NMNI, Belfast.
Waring, P. & Townsend, M. (2009). 2nd edition. Field Guide to the Moths of Great Britain and Ireland. British Wildlife.

Text written by:
Allen & Mellon