Empty nuptial gifts: a further step in the evolution of deception in spiders?

In the spider families Trechaleidae and Pisauridae, males offer nuptial gifts to females during courtship. Nutritive gifts contain recently caught prey wrapped in silk, while worthless gifts contain prey leftovers or plant parts. The presence of wrapped gifts is known in three out of 16 genera (ParatrechaleaCarico, 2005, Trechalea Thorell, 1869 and TrechaleoidesCarico, 2005) in Trechaleidae, suggesting that this sexual trait is of widespread occurrence in the family. Here, we report the presence of wrapped nuptial gifts in the genus Paradossenus F.O. Pickard-Cambridge, 1903. Males of P. longipes (Taczanowski, 1874) produce prey-gifts following the same sequence of behavioral units as described for other species of the family. More surprisingly, these males may also produce empty gifts consisting of a silken structure lacking contents. This is the first record of empty nuptial gifts in spiders. This novel male tactic may have evolved from worthless gifts as a further step in the evolution of deception in gift-giving spiders.