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Most of the living things that make up aeroplankton are very small to microscopic in size, and many can be difficult to identify because of their tiny size. Scientists can collect them for study in traps and sweep nets from airplanes, kites or balloons.
The aeroplankton comprises numerous microbes, including viruses, about 1000 different species of bacteria, around 40,000 varieties of fungi, and hundreds of species of protists, algae, mosses and liverworts that live some part of their life cycle as aeroplankton, often as spores, pollen, and wind-scattered seeds.
A large number of small animals, mainly arthropods (such as insects and spiders), are also carried upwards into the atmosphere by air currents and may be found floating several thousand feet up. Aphids, for example, are frequently found at high altitudes.
Many species of spiders deliberately use the wind to propel themselves around an area. The spider will find a vantage point (such as a branch, fence or surface) and, pointing its abdomen upward, eject fine threads of silk from the spinnerets. At some point, the friction of the air upon the silk thread(s) is great enough to get the spider lifted into the air and carried off by the breeze. This is called ballooning. Ballooning spiders (see Linyphiidae) are capable of drifting many miles away from where they started. The flexibility of their silk draglines can aid the aerodynamics of their flight, causing the spiders to drift an unpredictable and sometimes long distance .
- A. C. Hardy and P. S. Milne (1938) Studies in the Distribution of Insects by Aerial Currents. Journal of Animal Ecology, 7(2):199-229