for the many rich discussions on systematics and morphology, and for their valuable friendship and support. Special thanks to Yuji and André for his generosity and intelligent advice and to João for his spontaneity and continuous encouragement. I am specially thankful to Dr. Gustavo Hormiga for receiving me at the George Washington University and sharing with me ideas, advice, literature and encouragement. Thanks to Ligia Benavides, Jesus Ballesteros, Thiago Moreira, Daniela Andriamalala and Bob Kallal for their patient and help at Hormiga Lab. I deeply thank Ligia for hosting me in Washington and for her help and support.