The simplest method is to hand-sort samples under a stereo microscope. Brushing or shaking clothes and bedding etc into plastic bags usually produces only small numbers of specimens, but gives a reasonable representation of the taxonomic groups present.
Vacuum sampling is a convenient way to collect from fabric, e.g., upholstery, carpets, curtains and bedding. Samplers comprise a collecting tube or sleeve attached to the end of a vacuum cleaner nozzle. The tube incorporates a mesh to trap the dust. More simply, a gauze ‘sock’ can be fixed inside the nozzle.
Mobile mites can be driven out of loose fabric and rugs by the heat escape method. Lay the material on a slowly warming hotplate and weight down a piece of adhesive plastic (sticky side down) on its upper surface. As the hotplate heats up, the humidity within the sample gradually reduces and live mites are driven onto the adhesive. The plastic is removed and examined under a stereo microscope. The mobility test is similar to the latter, but no heat is applied. Instead, the sample is left for 24 hours. A heat attractant trap collects mites from fabric that cannot be accessed from both sides, e.g., mattresses and fitted carpets. Lay a piece of adhesive tape (sticky side down) on the study area, place a hot-water bottle (providing a temperature of about 40°C) over that and cover with a blanket to keep the heat in. Leave for up to 12 hours, overnight is ideal. The temperature in the trap is not so high that it significantly decreases humidity, but is enough to increase the mites’ activity so that they move towards the heat source and get caught on the tape.
Acari can also be extracted using funnel-desiccation (as described in Extracting specimens from habitat samples), suspension or flotation techniques. A simple suspension extraction involves spreading out the dust in a shallow glass dish, covering with 50-60 per cent lactic acid containing a few drops of lignin pink and heating at 60-70°C for about 30 minutes. Lignin pink stains chitin and so any mites present will be highlighted in various shades of pink. Flotation methods separate out specimens by exploiting the difference in densities between two liquids. For example, soak dust samples in 80 per cent ethanol for at least four hours, add a saturated sodium chloride (NaCl) solution and mix thoroughly. The mites float to the surface.