The I. posita-complex is revised. I. acicularis Donnelly, 1965 is considered a ssp. of posita, and I. p. atezca ssp. n. is described and figured (holotype $, allotype $: Mexico, Hidalgo, Molango, Laguna de Atezca, alt, 1400 m; 13-111-1988; deposited at Insectario, Univ. Xochimilco, Mexico).