Deliberations on the External Morphology and Modification of the Labial Segments in the Nepomorpha (Heteroptera: Insecta) with Notes on the Phylogenetic Characteristics
Shapes of the labial segments of the Pleidae. (a)–(d) Paraplea frontalis. (a) Dorsal view of the labium, the first segment is a narrow strap with the open stylet groove (gr), the second segment is divided into the triangular plate (tp) and the convex plate (cp), the triangular plate possess two pairs of nodules (no), the III segment is tubular, the IV segment is conical, the stylet groove is closed in these segments, (b) ventral view (V) of the labium, on the distal edge of the first segment (I) and the proximal edge of the fourth segment there is the midventral condyle (cv), the triangular apical plate can be observed, (c) the shape of the II segment, detailed view (D), the proximal part (no) of the triangular plate is slightly raised, and (d) the articulation between the second and third segments (cd) consists of three corners (condyles), the cor3 is distinctly protruding, there are no intercalary sclerites on the third segment (loss).
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