Larvae of Amblyomma cajennense (Fabricius, 1787), were obtained under laboratory conditions. The larvae were killed in hot water, preserved in 70o ethanol and prepared in definitive whole mounts. Two hundred larvae were examined under brightfield microscopy with an immersion objective in order to analyze the variation of the number of internal setae of the right and left side of the Haller’s organ chamber with the purpose of utilize them as chaetotaxy parameter for specific diagnosis.