To add to their difficulty, many species are often quite variable in background colouration on both sets of wings, have rather diffuse or indistinct markings (if any) and to add further difficulty, often have melanic forms to make identification even more impossible.

Some species though, are more straight-forward and easy to identify.

While all Pugs have a characteristic resting posture, which will enable easy recognition, there are a couple of common moths which possibly may cause confusion. Single-dotted Wave (Idaea dimidiata) and Small Dusty Wave (Idaea seriata) are two examples of moths which resemble most Pugs in resting posture.

Pugs belong to the sub-family Larentiinae (Carpets, Pugs and allies) which is found within the family Geometridae. Most Pugs belong to the Genus Eupithecia, although there are single examples of Gymnoscelis and Chloroclystis, along with two representatives of the Genus Pasiphila. Although Dentated Pug (Anticollix sparsata) has been recorded from Nottinghamshire, it differs structurally from the true Pugs, by lacking any sclerotised plate on the underside of the abdomen and is not listed in the species list below.

A total of 42 species of Pug are presently on the Nottinghamshire moth list. But Nottinghamshire and most other UK counties recently lost two Pug species from their county lists, when both Ash Pug and Ling Pug (formerly regarded as being seperate species in their own right) were reclassified as being forms of Angle-barred Pug and Narrow-winged Pug respectively.

The scientific species names, numbering system and order of species, are those used in the Checklist of the Lepidoptera of the British Isles (D. Agassiz, S. Beavan, R. Heckford. 2013). The old Bradley and Fletcher numbers are shown in grey.