SETAL ENTANGLEMENT - AN UNDESCRIBED METHOD OF STRIDULATION BY A NEOTROPICAL TARANTULA (ARANEAE, THERAPHOSIDAE)

The theraphosid spider Theraphosa leblondi (Latreille) produces a sibi lant, hissing sound during defensive displays. This sound is produced using a previously undescribed method of stridulation: setal entanglem ent. The opposing surfaces of the femora of the pedipalps, first, and second pair of legs are clothed in unique setae which have their dista l portion bearing hooks and a shaft clothed in filaments. Experimental ablations described here showed these plumose setae to be the site of sound production. Based on examination of the fine structure of these setae, we propose that the hissing sound is produced by the entanglem ent and pulling apart of the hooks at the ends of the setae on one leg surface and the long, plumose filaments on the median part of the set ae on the opposing leg surface. Evidence presented suggests that this is a case of an acoustic aposematic display directed at vertebrate pre dators.