ANTIPREDATOR DEFENSES OF PSILOCHORUS-SPHAEROIDES AND SMERINGOPUS-PALLIDUS (ARANEAE, PHOLCIDAE), TROPICAL WEB-BUILDING SPIDERS

Anti-predator defence behaviours of Psilochorus sphaeroides from Queensland and Smeringopus pallidus from Sri Lanka were studied in the laboratory. Whirling, in which these web-building pholcid spiders move their bodies rapidly around in circles, with legs remaining on the silk, is the most frequent response of adults to disturbance. Experiments were carried out to determine what types of stimuli elicited whirling. Forceful tactile and air movement stimuli elicited whirling, but there was no evidence that chemical stimuli from potential predators were important. Tactile stimulation was more effective than air movement. The behaviour of these pholcids was compared to that of a cosmopolitan pholcid, Pholcus phalangioides.