Whilst many spiders can be identified with "relative" ease using a low power binocular microscope with only one or two reference books and a small proportion can be identified in the field or from photographs, there are a number of groups within the spiders where the species are very similar and difficult to distinguish. PDF documents are available below, produced by experienced arachnologists, which aim to help all arachnologists to correctly identify the species with these groupings.

Below are links to the first selection of Difficult Species Crib Sheets (these are all PDFs and should open into a new window or tab):

Identification of Alopecosa cuneata and pulverulenta
Identification of Bathyphantes gracilis and Bathyphantes parvulus
Identification of Centromerita bicolor and C. concinna
Identification of Clubiona neglecta and Clubiona pseudoneglecta
Identification of Clubiona rosserae
Identification of Dictyna species
Identification of Drassodes cupreus and D. lapidosus.pdf
Identification of Dysdera crocata and erythrina
Identification of Entelecara acuminata and Entelecara congenera
Identification of females of British Oedothorax species
Identification of Neon robustus and Neon reticulatus
Identification of Pardosa lugubris sens. str. and P. saltans
Identification of Pelecopsis nemoralis and P. nemoralioides
Identification of Philodromus praedatus and P. aureolus
Identification of Pocadicnemis pumila and P. juncea
Identification of Porrhomma species
Identification of Tegenaria gigantea and saeva
Identification of Tetragnatha extensa and Tetragnatha pinicola
Identification of Xysticus audax and X. cristatus.pdf
Identification of Zelotes apricorum and subterraneus

The intention is to add to these as more become available.