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 Notonectidae. Notonectinae. (a)–(d). Notonecta glauca. (a) Dorsal view on the segments: the first segment is wide, the stylet groove is covered by the labrum, the base of the second segment possesses the open stylet groove (gr), (b) dorsal view of the labium, the shape of the second segment is that of a triangular plate (tp) with a distinctly visible nodule (no) and a convex plate (cp), the articulation between the second and third segments (cd), (c) the third segment is tubular, the stylet groove (gr) is closed, (d) the fourth segment is conical, the stylet groove (gr) is closed, (e) ventral view (V) of the segments, the first segment on the distal edge has a midventral condyle (cv), this segment is narrower ventrally than dorsally, (f) ventral view (V), the III segment is tubular, and (g) the IV segment is conical, the stylet groove is closed in this segment, on the fourth segment there is situated the midventral condyle (cv) but it is only slightly visible (circle), the apical plate can be observed. Lr: labrum, Pp: posterior plate of the cranium.
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