As many species of molluscs are relatively small a good set of sieves is an almost essential item of a conchologists armoury and are regularly used both in the field and at home. The precise use depends on the habitat being explored but they are particulary useful for searching sediment, leaf litter (in a terrestrial environment) or, in a marine environment weed washing or the results of boulder scrubbing.
The basic idea is that using a range of meshes it is possible to grade habitat smaples (leaf litter, weed, sediment etc.) so that large specimens and vegetation can be examined separately from the finer fractions where the smaller species will be picked up. However, the sievings from very fine mesh can be very difficult to search in the field due to the quantity of material or the very small size of the species being looked for. This type of fine material is best checked under a microscope in very small quantities.
There are a range of options, depending on budget.
Metal test sieves
Definitely the best option but relatively expensive (at least £50 each). A range of mesh sizes is useful - typically 4mm and 0.5mm being the most heavily used - and a diameter of 20cm is ideal for use both in the field and the lab. If the sieves are well cared for they will last well though if working in a marine environment it is advisable to go for stainless steel.
Suppliers:
- Endecotts Ltd,. 9 Lombard Road, LONDON SW19 3UP; Tel. 020 8548121.
- Fisher Scientific UK, Sales Department, Bishops Meadow Road, LOUGHBOROUGH, Leics LEl 1 5RG; Tel. 01509 231166; Fax:01509 231893. Endecotts Ltd. test sieves; minimum order £50 the approximate cost of one quality stainless steel sieve (If you telephone them they will send a photocopy of the relevant page(s) from their bulky catalogue).
- Geo Supplies Ltd. 49 Station Road, Chapeltown, SHEFFIELD S35 2XE Tel. 0114 245 5746.
Plastic test sieves
These are less durable than the metal variety but significantly cheaper; typically a set of six will cost the same as a single metal sieve.
Suppliers:
- Geo Supplies Ltd. 49 Station Road, Chapeltown, SHEFFIELD S35 2XE Tel. 0114 245 5746;
Build your own
If your budget is tight you might consider building your own sieves. The materials required are:
- 2m of 45mm X 7mm wood (free from knots)
- 2m of 30mm X 15mm wood (free from knots)
- 2m of 15mm X 15mm triangular beading
- Evo-Stick (or similar) adhesive. Note that it needs to be able to withstand constant submersion but not dissolve the nylon.
- Panel pins
- 1 piece of Nybolt nylon mesh (NYL 9125-2000.MIC10, GG-ASTM NYL )
- 1 piece of Nybolt nylon mesh (NYL 9166 PA-30GG-670 NYTAL)
Ensure the joints are cut squarely and accurately as shown in the sketch. Cut four length of 250mm and four of 150mm of the 45mm X 7mm wood. Glue and pin the joints together to form the outer frames. Then cut the 30 X 15mm wood to create two frames to fit snugly within the frames already made. The inner frame should be tapered slightly to ease the stacking of the finished sieves. Glue the inner frames to the outer frames ensuring that there is 15mm of overlap (this needs to be done fairly precisely). Next cut and glue the nylon mesh onto the top of the inner frame and cut the triangular beading and glue and pin this on top of the mesh. The beading should be mitred at the corners to ensure a tight fit with no gaps (otherwise there is a risk of specimens getting lost in the corners). Paint or varnish the wood to protect from damp conditions. Using a light colourder paint will make it more obvious in the field.
Suppliers:
- John Staniar & Co., 34 Stanley Road Whitefield, MANCHESTER, M45 8QX . Tel: 0161 767 1500 (Sales). Supply the nylon mesh