Identification of arachnids other than spiders often requires special preparation.

(a) Spiders, non-hydracarine mites, and the larvae of water mites: specimens from these groups may be preserved in 70-80% ethanol. Non-hydracarine mites should be cleared in lactic acid or Nesbitt's Fluid, and then placed in glycerol in a cavity slide for examination under a compound microscope. Permanent mounts can be made with Hoyer's Fluid or polyvinyl alcohol preparations (Krantz 1978).

(b) Nymphal and adult Hydracarina: these mites often make poor specimens if they are stored in ethanol for longer than a few days. Formalin is an even worse presevative as it makes the body of the mite rigid and difficult to clear. Ideally, water mites should be killed, preserved and stored in Koenike's Fluid (10% glacial acetic acid, 50% glycerol, 40% water), also known as GAW (Harvey 1998). This preservative keeps mites soft and flexible, and allows them to retain some of their original colour patterns. Water mites that have been briefly exposed to ethanol usually make good specimens if they are rapidly transferred to Koenike's Fluid and left for several days to soften.

Although many families and subfamilies of water mites can be identified from uncleared specimens, most require clearing. Water mites are cleared in a solution of 10% KOH, and are returned to Koenike's Fluid when the body contents have become transparent. If examination under a compound microscope is necessary, the body contents of the mite should be expelled through a small hole torn in soft membranes, and the deflated body of the mite arranged in a glycerine-filled cavity slide so that all appendages are visible (this may require dissection). High quality permanent mounts of water mites are made in glycerine jelly (Cook 1974).