In addition to an assessment of the status of each species within the Upper Thames area, this website also provides the status of each species in a Great Britain context, using the latest information, status reviews and under the relevant legislation.

1. Red List statuses

UK species conservation status designations are based on categories and criteria first produced in the 1980s for the International Union for the Conservation of Nature (IUCN) (now called the World Conservation Union) RED LIST. The aim was to assess the threat of extinction to species of all taxa. The criteria were subsequently revised, most recently in August 2010. In the UK, the system was first adopted in the Red Data Books (Shirt, 1987, etc.).

Individual countries are permitted to refine the definitions in the Lower Risk categories. The new criteria were adopted by JNCC in 1995, and are the basis of all reviews of taxon groups in the UK published since that date. The criteria are lengthy and are not included here, but include measures of decline as well as rarity. The resultant categories include the familiar Red Data Book (1, 2 and 3) and Nationally Scarce Notable A/B.

More recently, reviews of various invertebrate groups have been carried out in the UK using the IUCN RED LIST criteria, based more on decline and risk of extinction. The IUCN criteria are lengthy and are not given here, but are accessible via the IUCN website (see references). Alongside these categories, revised GB Rarity Statuses have been produced these as part of the reviews, with modified categories. Resident macro-moths have very recently been through this process (Fox et al, 2019). For micro-moth statuses see section 2c.

The RED LIST category definitions are (after Fox et al, 2019):


A taxon is Extinct when there is no reasonable doubt that the last individual has died. In the macro-moth review, species not recorded in GB this century are considered Regionally Extinct.


A taxon is Critically Endangered when the best available evidence indicates that it meets any of the IUCN criteria for Critically Endangered. ‘Possibly Extinct’ is an additional tag used for Critically Endangered taxa that are, on the balance of evidence, likely to be extinct, but for which there is a small chance that they may be extant.


A taxon is Endangered when the best available evidence indicates that it meets any of the IUCN criteria for Endangered.


A taxon is Vulnerable when the best available evidence indicates that it meets any of the IUCN for Vulnerable.


A taxon is Near Threatened when it has been evaluated against the criteria but does not qualify for Critically Endangered, Endangered or Vulnerable now, but is close to qualifying for or is considered likely to qualify for a threatened category in the near future.


A taxon is Least Concern when it has been evaluated against the criteria and does not qualify for Critically Endangered, Endangered, Vulnerable or Near Threatened. Widespread and abundant taxa are included in this category.


A taxon is Data Deficient when there is inadequate information to make a direct, or indirect, assessment of its risk of extinction based on its distribution and/or population status. A taxon in this category may be well studied, and its biology well known, but appropriate data on abundance and/or distribution are lacking. Data Deficient is therefore not a category of threat. Listing of taxa in this category indicates that more information is required and acknowledges the possibility that future research will show that threatened classification is appropriate.


A taxon that is deemed to be ineligible for assessment at a regional level is listed as Not Applicable. This can be for a variety of reasons e.g. because it is not within its natural range in the region or because it is a vagrant to the region. In this review, GB species that are resident because of human introduction are considered Not Applicable. 


A taxon is Not Evaluated when it has not yet been evaluated against the criteria.

2a. GB RARITY STATUSES (after Fox et al, 2019) as applied to macro-moths


Native species recorded (as resident breeding species) from 15 or fewer hectads (10 km x 10 km grid squares) of the GB Ordnance Survey national grid in the period 2000-2014 and where there is reasonable confidence that exhaustive recording would not find them in more than 15 hectads. This category includes species that are probably extinct.


Native species that are not regarded as Nationally Rare and which have not been recorded (as resident breeding species) from more than 100 hectads of the GB Ordnance Survey national grid in the period 2000-2014 and where there is reasonable confidence that exhaustive recording would not find them in more than 100 hectads.

Importantly, Nationally Rare and Nationally Scarce are not categories of threat.


2b. Other existing GB statuses used on this website but not defined by Fox et al (2019)

Common - too frequent, widely distributed and found in a wide range of habitats to qualify as Nationally Scarce or Nationally Rare. Note that here, this includes some macro-moth species previously listed as “Local” (see also 2c, below).    

Immigrant – species that are known to migrate to the British Isles, but which do not normally survive the winter. Note that this does not include resident species that are also recognised as being immigrant. Immigrant (non-breeding) species are not assessed by Red Lists.

Unknown – species about which insufficient is known to assign them to one of the above categories.

Naturalised – species that have been artificially introduced and now breed successfully in the wild.

Adventive – originating outside the British Isles and usually found with imported goods or in their vicinity.

2c. GB rarity statuses (as applied to micro-moths and formerly to macro-moths).

Micro-moths have yet to be Red listed and their status is that proposed by Davis (2012). Before the 2019 review, rarity categories for macro-moths were the same as those applied by JNCC to other invertebrate groups. The former rarity status of all the macro-moth species found in the Upper Thames region is to be found on the species list page of this website and equates to those given in Waring, Townsend and Lewington (2017).

This website does not yet feature micro-moths, but it is hoped that it will do so in the future. Unless a Red List review of micros takes place in the meantime, the current statuses will be listed on the website.

Red Data Book 1 (RDB1). Taxa in danger of extinction and whose survival is unlikely if the causal factors continue to operate. These include: Species only known from a single locality since 1970 Species restricted to habitats which are especially vulnerable. Species showing a rapid and continuous decline in the last 20 years and now estimated to exist in ≤ 5 localities.

Red Data Book 2 (RDB2). “Vulnerable”. Taxa believed likely to move in to the “Endangered” category in the near future if the causal factors continue to operate. These include: Species declining throughout their range. Species in vulnerable habitats. Species whose populations are low.

Red Data Book 3 (RBD3). “Rare”. Taxa with small populations that are not at present endangered or vulnerable but which are at risk. These include: Species estimated to occur in 15 or fewer localities.

Red Data Book I (RDBI) “Indeterminate”. Taxa considered to be Endangered, Vulnerable or Rare, but there is not enough information to say which of the three categories is appropriate.

Red Data Book K (RDBK). Taxa suspected to fall within the RDB categories but which are at present insufficiently known to enable placement.

Nationally Scarce (Notable, N) – estimated to occur in 16-100 10km squares (applied to Diptera only). Nationally Scarce (Notable A, Na) – estimated to occur in 16-30 10km squares.                        

 Nationally Scarce (Notable B, Nb) – estimated to occur in 31-100 10 km squares.

Local – occurs in 101 – 300 10km squares. This category had ceased to be officially recognised even before Red List reviews, but is used by Davis (2012). In the recent review of macro-moths, distribution data was not evaluated against the Local criterion. The status is provided in the species list, but the data used to assign species to this status is considered to be very out-of-date.

3. NERC Act Section 41 (S41) Species

In addition to GB statuses, this website also provides the current status of species under the Biodiversity Action Plan process and subsequent processes.

The UK Biodiversity Action Plan (UK BAP) was published in 1994, and was the UK Government’s response to the Convention on Biological Diversity (CBD), which the UK signed up to in 1992 in Rio de Janeiro. The CBD called for the development and enforcement of national strategies and associated action plans to identify, conserve and protect existing biological diversity, and to enhance it wherever possible (source

UK BAP Priority Species and Habitats were those that were identified as being the most threatened and requiring conservation action under the UK BAP. The original lists of UK BAP priority species and habitats were created between 1995 and 1999, and were subsequently updated in 2007, following a 2-year review.

The BAP species are now known as SPECIES OF PRINCIPAL IMPORTANCE (S41 species) under Section 41 species of the Natural Environment and Rural Communities (NERC) Act 2006, as part of the UK Post-2010 Biodiversity Framework. This includes BAP(R – research only) - a tranche of larger moths, identified after analysis of data from the network of Rothamsted light traps as common and widespread but declining. They were added to the UK BAP list in 2007 as a separate tranche, in order to generate research into their declines.  

4. Wildlife and Countryside Act (1981 and as amended) species

It is an offence to kill, injure, possess or sell any life stage of the moth species legally protected under Schedule 5 of the WCA, or to damage or destroy their habitat.




Davis, A.M. 2012. A Review of the Status of Microlepidoptera in Britain. Butterfly Conservation, Wareham. (Butterfly Conservation Report No. S12-02). Butterfly Conservation, Lulworth.

Fox, R., Parsons, .M.S. and Harrower, C.A. 2019. A review of the status of the macro-moths of Great Britain. Butterfly Conservation Report Number S19-17. Butterfly Conservation, Lulworth. (Available via the Butterfly Conservation website, with references to IUCN categories).

Shirt, D.B. (ed.) (1987) British Red Data Books: 2: Insects. Joint Nature Conservation Committee, Peterborough.

Waring, P., Townsend, M.C. and Lewington, R. 2017. Field Guide to the Moths of Great Britain and Ireland (third edition). Bloomsbury, London.