identification of spiders

  1. Proper identification of the majority of spiders relies on the use of a microscope (preferably a stereo instrument), a powerful top light, and reliable reference texts. Many of the species on the British list are very small, just a few millimetres in length. Also, identification of nearly all spiders requires careful examination of tiny morphological features. A standard reference text on British spiders is required - The Spiders of Great Britain and Ireland, 3 volumes, by M. Roberts; British Spiders, 3 volumes, by Locket and Millidge and Locket, Millidge and Merrett. These items are all rather expensive. A cheaper alternative is the Collins Field Guide Spiders of Britain & Northern Europe by Michael J. Roberts, but this does not cover all the species, principally not the Linyphiidae or 'money spiders'. Some experience of using a microscope and dichotomous keys is essential. A determination key to family, genera and species of Central European spiders available at link may be of additional use, but of course includes a great many spiders not recorded in Britain. Special attention should be paid to those species that are rare or uncommon. Full details of date, site, habitat and status should be noted, and specimen(s) should be sent to the appropriate Area Organiser for verification. They in turn may seek further help from other experts before returning the specimens to the Recorder.
  2. Recorders should normally retain voucher specimens. This enables valuable information to be obtained when, for example, it is realised that what had been regarded as a single species is, in fact, composed of two or more species (e.g. as with Enoplognatha ovata/latimana, Meioneta saxatilis/mossica, Walckenaeria antica/alticeps). A collection should be organised along the lines recommended by John Cooke in the Bulletin of the British Spider Study Group, 32: 1-3. Voucher specimens are needed to ensure that no errors are made in identifying the species. This problem tends to be greater for the rarer species because collectors/recorders do not have many specimens with which to make comparisons. In almost all cases, specimens can be collected without making any significant difference to the population: collecting has a minute impact compared with natural mortalities and the loss of habitat to unsympathetic management, modern agricultural practices and various land developments. Species should be collected with restraint, and Dolomedes plantarius and Eresus sandaliatus are protected under schedule 5 of the Wildlife and Countryside Act and may not be collected without a licence from the Joint Nature Conservation Committee. For these species, and perhaps for a few others where collecting may be feared to endanger the population, corroboration of the record in the form of a good quality photograph with detailed notes would be welcome. If possible, note enough detail to enable the site to be located again so that, if necessary, a visit by an experienced arachnologist could be arranged.
  3. In the early stages of involvement in the Scheme a Recorder may be asked to supply named specimens, in support of their records of some of the 'common' and 'frequent' species, until such time as their competence has been established by the Area Organiser. Rare species or species outside their known range should in any case be checked by another competent arachnologist. If it is necessary to send a specimen to an Area Organiser for checking please remember that damage can be caused if it is incorrectly packaged for posting. The following guidelines should be adhered to:
    • i). Place the specimen in a small tube with a well-fitting plastic stopper or screw top. Either fill the tube completely with liquid (to prevent mechanical damage by air bubbles during transit) or restrain movement of the specimen using a small piece of tissue such as part of a paper hankerchief or kitchen paper. Cotton wool should not be used for this purpose, as the cotton strands become entangled with the spider.
    • ii). Write clearly in pencil or alcohol-proof and waterproof ink (e.g. "Rotring" or Pilot water resistant drawing pen) on a label that is placed inside the tube with the specimen. Do not label the outside of the tube. If the tube leaks such labels are often rendered illegible, or, if the label is lost, the material becomes worthless. All tubes should contain a label containing the minimum information of location, grid reference, date, collector.
    • iii). Indicate if the liquid in the tube is other than 70% alcohol. Avoid the use of glycerine which can stick trichobothria to the surface of the legs, making them very difficult to locate. If iso-propyl alcohol is used rather than Industrial Methylated Spirits, then 50- 60% dilution is recommended to avoid the specimens becoming brittle.
    • iv). The tube containing the specimen should be protected by using a hollowed-out block of polystyrene, a tin lined with cotton wool or paper padding, or plenty of bubble wrap inside a box or padded envelope.
    • v). Remember that a covering letter written in ink or ball-point may be rendered illegible if the tube leaks during transit.
    • vi). If specimens are to be returned then stamps to the appropriate value should be enclosed.
  4. Spiders are collected into, and then stored, in 70% alcohol (Industrial Methylated Spirits) in which they do not decompose. They are examined using the microscope whilst immersed in alcohol. They are then static for the close inspection that is needed and the identification can be checked at a later date if necessary. Very few species can be identified with confidence by simply observing them in the field or from photographs.
  5. The value of building and maintaining a personal reference collection of correctly identified species cannot be overemphasized. With such a reference collection, direct comparisons can be made, especially important for critical and difficult species.
  6. Identification Difficulty values have been assigned to each British species to provide some guidance on what is needed for reliable identification.
  7. Membership of the Spider Recording Scheme is unlikely to be suitable for young children - on the other hand the British Arachnological Society aims to encourage and help youngsters with an interest in spiders - contact the Membership Secretary through the BAS website link, where you can also join on-line or by post.