Crabro flavipennis basiflavus Brèthes, 1910:282 - As Ectemnius basiflavus: - Callan, 1991Callan, E.Mc C. 1991. Sphecidae of Trinidad. III. Crabroninae, Nyssoninae and Philanthinae. Sphecos 21:8-12. (distribution); Amarante, 2002Amarante, S.T.P. 2002. A synonymic catalog of the neotropical Crabronidae and Sphecidae (Hymenoptera: Apoidea). Arquivos de Zoologia (São Paulo) 37:1-139. (distribution); Starr & Hook, 2003Starr, C.K. & Hook, A.W. 2003. The aculeate Hymenoptera of Trinidad, West Indies. Occasional Papers o the Department of Life Sciences, University of the West Indies 12:1-31. (distribution); Leclercq, 2007Leclercq, J. 2007. Hyménoptères Crabroniens des Amériques du genre Ectemnius Dahlbom 1845 (Hymenoptera: Crabronidae Crabronini). Notes fauniques de Gembloux 60 (4):163-177. (distribution); Rasmussen & Asenjo, 2009Rasmussen, C. & A. Asenjo 2009. A checklist to the wasps of Peru (Hymenoptera, Aculeata). ZooKeys 15:1-78. (distribution).
Xylocrabro umbrosus Schrottky, 1914:624 - Amarante, 2002Amarante, S.T.P. 2002. A synonymic catalog of the neotropical Crabronidae and Sphecidae (Hymenoptera: Apoidea). Arquivos de Zoologia (São Paulo) 37:1-139.:27 ( listed as synonym of Ectemnius basiflavus (Brèthes, 1910)).
Ectemnius cassus Leclercq, 1956:304 - Amarante, 2002Amarante, S.T.P. 2002. A synonymic catalog of the neotropical Crabronidae and Sphecidae (Hymenoptera: Apoidea). Arquivos de Zoologia (São Paulo) 37:1-139.:27 ( listed as synonym of Ectemnius basiflavus (Brèthes, 1910)).