Tettigonioids typically deposit their eggs within the substrate, whether in the soil or in plants. Consequently, these eggs often exhibit a rounded shape with a relatively smooth surface. Despite this, various studies have consistently demonstrated that egg shape is a stable characteristic within species, differing between distinct groups. However, to date, no comprehensive comparative analysis has been conducted, even though regional studies have suggested that the eggs of Phaneropterinae differ from all others. In this study, we present data on the length, width, and height of 352 species and subspecies, including measurements for 158 species that were newly assessed. Our findings substantiate the claim that the eggs of the Phaneropterinae subfamily can be distinguished by their flattened shape. Based on this important and diagnostic characteristic, we advocate for the re-transfer of the genus Brinckiella into Meconematinae. We propose a hypothesis suggesting that the evolution of the flattened egg shape in Phaneropterinae may have conferred advantages during the adhesive process of attaching eggs to plants—an assumed ancestral method of oviposition in this subfamily. Subsequently, these flat eggs found their way onto leaves or into the ground. While some other subfamilies exhibit eggs conforming to the basic tettigonioid shape, they showcase distinct features (e.g., Pseudophyllinae, Mecopodinae). We anticipate that future investigations into the lesser-explored Meconematinae, focusing on the small eggs and the oviposition behavior within this subfamily, will yield intriguing insights.