Mason (1981) erected Illidops to accommodate a group of species with the lower margin of the eyes converging and metasomal terga 3–7 weakly sclerotized. However, those characters are not universal within the genus, being absent in several species. This might be one reason why the genus has not been universally recognized. After studying species from different regions of the world, Fernández-Triana et al. (2014) reported features that permit a better definition of the genus Illidops, such as a band of rugosity centrally on the posterior edge of the scutellar disc; a shortened fore wing vein R1; and propodeum fully sculptured but without areola (instead, with a series of short carinae medially on the posterior 0.2–0.3 of the propodeum near the nucha). DNA barcoding tends to clearly cluster species of Illidops and Apanteles separately (e.g. Smith et al. 2013).
Mason (1981) erected Illidops to accommodate a group of species with the lower margin of the eyes converging and metasomal terga 3–7 weakly sclerotized. However, those characters are not universal within the genus, being absent in several species. This might be one reason why the genus has not been universally recognized. After studying species from different regions of the world, Fernández-Triana et al. (2014) reported features that permit a better definition of the genus Illidops, such as a band of rugosity centrally on the posterior edge of the scutellar disc; a shortened fore wing vein R1; and propodeum fully sculptured but without areola (instead, with a series of short carinae medially on the posterior 0.2–0.3 of the propodeum near the nucha). DNA barcoding tends to clearly cluster species of Illidops and Apanteles separately (e.g. Smith et al. 2013).