Meteorological Aspects of Aeronautic Behaviour of Spiders

An analysis was made of the meteorological circumstances under which spiders travel through the air (aeronautic behaviour). The research was done by relating numbers of spiders captured from the vegetation (i.e. spiders attempting to get airborne) and of those captured from the air to meteorological parameters. During periods with activity it was found that the numbers of spiders transported into the air are highly dependent on the instability of the air above the vegetation. This was demonstrated by means of a stability ratio. Furthermore it was shown that increase of the wind velocity limits the activity in different ways. The relation of the incidence of activity with some meteorological parameters was investigated. The incidence of such activity on a certain day depends on the wind velocity, and the probable frequency of incidence can be estimated by an aeronautic index. It could not be concluded that the start of behaviour is stimulated by any particular meteorological factor.