Comparative Wing-Scale Ultrastructure Reveals Distinct Structural Modifications Associated with Transparent Wing Regions in Two Moth Species (Lepidoptera)

Transparent wings are a striking morphological feature in Lepidoptera, yet the scale modifications associated with transparency remain insufficiently understood in many moth groups. In this study, we qualitatively examined the ultrastructure of scales from transparent and opaque wing regions in two moth species, Amata emma (Butler) (Erebidae) and Thyrassia penangae (Moore) (Zygaenidae), using scanning electron microscopy (SEM). In the examined transparent regions of both specimens, substantial areas of the wing membrane remained exposed between scales, but the scale morphologies differed markedly. In A. emma, transparent-region scales were elongated, narrow, and needle-like, whereas those of T. penangae projected from the wing membrane and exhibited a distinctive bud-like morphology with folded distal lamellar structures. Opaque-region scales in both specimens were broad, leaf-shaped, and arranged in an overlapping pattern, with conspicuous perforations between longitudinal ridges. Longitudinal SEM observations further revealed a shared hollow internal architecture consisting of upper and lower laminae interconnected by trabeculae, although trabecular morphology differed between scales from the transparent and opaque wing regions. These observations show that macroscopically similar transparent wing regions in the examined specimens can be associated with distinct scale-level structural modifications and highlight the diversity of scale architectures associated with wing transparency in Lepidoptera.