Ichneumonidae is the most speciose family within Hymenoptera. The incredible diversity of ichneumonids is reflected in the many different lifestyles and associated morphological characters. The Ophioniformes is a grouping of ichneumonid subfamilies which are defined as possessing a sub-apical dorsal notch located on the ovipositor. However, function related to this morphological character is unknown. Variation in the form of the sub-apical notch is surveyed within and outside the Ophioniformes, with emphasis on the Ctenopelmatinae. Comparisons are made with similar morphological characters in other families within Hymenoptera.