Literature describing experiments and theories on factors affecting spider ballooning is deficient and what does exist is often contradictory between authors. Most work has been done on the meteorological conditions at the time of take-off. The one factor that is widely agreed upon is the upper wind speed limit of 3 m/sec. Other factors considered important by some authors include thermal production, wind speed gradients, cloud cover, and humidity. Literature on the underlying motivation and instigation of pre-ballooning behaviour (climbing to a prominent point and silk release) is very limited and largely supposition. Temperature rise, temperature drop, humidity change, air movement, vibration, light intensity, and stress have all been suggested as initiation stimuli of ballooning behaviour. Habitat instability, dispersal strategy, mating, reduction of competition, and avoidance of cannibalism have been suggested as reasons for the evolution of ballooning behaviour by certain spider species. Spiders are important polyphagous predators on arable farmland and the high mobility of ballooning species means that they are often the first to arrive in a crop newly infested with pests, and have a role in controlling the outbreak until more specific predators arrive. In order to fully exploit the pest control potential of spiders on arable farmland more work is needed to gain a better understanding of factors controlling their distribution and movement.