ZOOLOGIA 30 (4): 403–418, August, 2013 http://dx.doi.org/10.1590/S1984-46702013000400006 Morphology, evolution and usage of urticating setae by tarantulas (Araneae: Theraphosidae) Rogério Bertani1,3 & José Paulo Leite Guadanucci2 1 Laboratório Especial de Ecologia e Evolução, Instituto Butantan. Avenida Vital Brazil 1500, 05503-900 São Paulo SP, Brazil. E-mail:
[email protected] 2 Laboratório de Zoologia de Invertebrados, Universidade Federal dos Vales do Jequitinhonha e Mucuri, Campus JK. Rodovia MGT 367, km 583, 39100-000 Diamantina, MG, Brazil. E-mail:
[email protected] 3 Corresponding author. ABSTRACT. Urticating setae are exclusive to New World tarantulas and are found in approximately 90% of the New World species. Six morphological types have been proposed and, in several species, two morphological types can be found in the same individual. In the past few years, there has been growing concern to learn more about urticating setae, but many questions still remain unanswered. After studying individuals from several theraphosid species, we endeavored to find more about the segregation of the different types of setae into different abdominal regions, and the possible existence of patterns; the morphological variability of urticating setae types and their limits; whether there is variability in the length of urticating setae across the abdominal area; and whether spiders use different types of urticat- ing setae differently. We found that the two types of urticating setae, which can be found together in most theraphosine species, are segregated into distinct areas on the spider’s abdomen: type III occurs on the median and posterior areas with either type I or IV surrounding the patch of type III setae.