Prohydrometra D. Polhemus, 2022

Polhemus, Dan A., 2022, Two new genera and six new species of Terrestrial Hydrometridae (Hemiptera: Heteroptera) from French Polynesia, Zootaxa 5190 (1), pp. 69-98 : 76

Prohydrometra D. Polhemus n. gen.

Figs. 9–29

Description. Body small for family, narrow (see J. Polhemus & D. Polhemus 1995a, Fig 1 ); body without black spicules; body lengths 4.15–7.20.

Color: Ground blackish-brown to yellowish-brown; legs slightly paler; abdominal laterotergites often with faintly suggested paler areas on anterior halves.

Structural characters: Head relatively long, anteocular portion slightly longer than postocular portion ( Figs. 10 , 12 ), ratio varying from 1.33/1.00 to 1.59/1.00; eyes small, with dorsal eye width subequal to or less than width of interocular space ( Figs. 10 , 12 ); labium long, reaching onto prosternum; antennae long, combined length equal to nearly that of body, slender, antennomere II longer than antennomere I, antennomere III over 5 times as long as antennomere II ( Fig. 11 ), antennomere IV about 3 times as long as antennomere II.

Thorax widened posteriorly; pronotal lobe short, extending posteriorly over mesonotum, metanotum exposed, without any trace of wing pads; acetabula without pits.

Legs slender, moderately long, combined lengths of hind leg segments about 1.3 times as long as body; foreto-middle versus middle-to-hind coxal spacing unequal, ratio varying from 1.00/1.22 to 1.00/1.90 ( Figs. 9 , 13 ); pretarsus with both dorsal and ventral arcuate arolia, parempodia long, setae-like.

Abdomen with segment I clearly delineated, short, rectangular; abdominal mediotergites II–VII rectangular, slightly longer than wide, length to width ratio about 1.1/1.0; female abdominal sternum VII and tergum VIII without caudal processes; male abdominal sternum VII bearing paired sclerotized processes or modified setal patches to either side of longitudinal midline ( Figs. 19–24 ).

Type-species. Hydrometra gagnei J. Polhemus & D. Polhemus, 1995a .

Etymology. The generic name Prohydrometra is derived from pro-, L., before, and Hydrometra , water measurer. Gender feminine.

Distribution. French Polynesia, Society Islands (Moorea, Raiatea, Tahiti).

Discussion. Prohydrometra possesses a set of character states that are intermediate between the putatively plesiomorphic conditions seen in Marquesametra , and the more modified states seen in Hydrometra . The abdomen is longer than in Marquesametra , in which the mediotergites are quadrate and equilateral, but shorter than in Hydrometra , with abdominal mediotergites III–VI weakly rectangular, being slightly longer than wide, but not nearly so elongate as in Hydrometra . The hind coxae are slightly more posteriorly displaced to varying degrees compared to the condition seen in Marquesametra , where the spacing is nearly equal (compare Figs. 3 , 9 , 13 ), but still far less asymmetrical than the condition seen in Hydrometra . The legs are longer longer than in Marquesametra , with the combined length of the hind leg slightly longer than the body, but shorter and less thread-like than in Hydrometra species. Similar to Marquesametra , but in contrast to Hydrometra , the body lacks both black spicules ventrally, and pits on the acetabula. The posterior pair of cephalic trichobothria is set on low tubercles, similar to Hydrometra species and the three endemic Marquesan genera, and the eyes are somewhat reduced, a character state also prevailing in the endemic Marquesan genera. This suite of characters, as well as those discussed previously under Marquesametra , serve to separate this genus from others in the family. In addition, the members of this genus have a diagnostic antennal morphology, with the combined lengths of the antennomeres being subequal to that of the body, due to a highly elongated antennomere III, which is five times the length of antennomere II ( Fig. 11 ).

Figures

FIGURE 1. Marquesametra hivaoa n. sp., dorsal habitus. Specimen from Marquesas Islands, Hiva Oa, Mt. Temetiu, CL 6031. Young Sohn illustration.

FIGURE 11. Prohydrometra johnpolhemi n. sp., head in lateral view, showing very long antennal segment III diagnostic for this genus. Specimen from French Polynesia, Raiatea, Trois Cascade, CL 7521.

FIGURES 9, 10. Prohydrometra gagnei, morphological details. 9. Male ventral left thorax, showing coxal spacing. 10. Male head, dorsal view, with positions of cephalic trichobothria indicated. Specimen from French Polynesia, Tahiti, Mt. Marau, CL 7498.

FIGURES 12–15. Prohydrometra englundi n. sp., female, morphological details. 12. Head, dorsal view, with positions of cephalic trichobothria indicated. 13. Ventral left thorax, showing coxal spacing. 14. Terminal abdomen, ventral view. 15. Left foreleg, ventral view. Specimen from French Polynesia, Raiatea, Mt. Toomaru.

FIGURES 16, 17. Photographs of habitat for Prohydrometra johnpolhemi n. sp. at Trois Cascade, Raiatea, CL 7521. 12. Second waterfall, flanked by wet rock faces on which the species occurred. 13. Dr. John T. Polhemus collecting specimens on wet rock faces lateral to the waterfall.

FIGURE 18. Distribution of Prohydrometra species in the western Society Islands. Triangle = P. johnpolhemi n. sp.; square = P. englundi n. sp.

FIGURES 19–24. Prohydrometra n. gen. species, male ventral terminal abdomen. 19. P. gagnei, specimen from Tahiti, Mt. Marau. 20. P. gagnei, specimen from Tahiti, Mt. Mauru, showing yellowish-brown coloration. 21. P. moorea n. sp., specimen from Moorea, Mt. Tohiea. 22. P. teatara n. sp., specimen from Tahiti, Mts. Teatara. 23. P. tohiea n. sp., holotype, specimen from Moorea, Mt. Tohiea. 24. P. johnpolhemi n. sp., specimen from Raiatea, Trois Cascade.

FIGURES 25, 26. Photographs of habitat for Prohydrometra n. gen. species on Moorea and Tahiti. 25. Mt. Tohiea summit area, CL 7500, habitat for P. moorea n. sp. and P. tohiea n. sp.. 26. Tahiti Iti, Mts Teatara, 1080 m. mossy Weimannia trees providing habitat for P. teatara n. sp..

FIGURES 27, 28. Photographs of habitats for Prohydrometra gagnei on Tahiti. 27. Mt Marau, fern gulley along road to summit, 1380 m., CL 7498, J. T. Polhemus collecting from a fogging sheet set below banks of ferns. 28. Mt. Mauru, banks of Dicranopteris ferns along trail to summit between Pylon 3 and Pylon 4, CL 7486.

FIGURE 29. Distribution of Prohydrometra n. gen. species in the eastern Society Islands. Triangle = P. tohiea n. sp.; circle = P. moorea n. sp.; squares = P. gangei; pentagon = P. teatara n. sp.

FIGURES 2–4. Marquesametra hivaoa n. sp., morphological details. 2. Male head, dorsal view, with positions of trichobothria indicated. 3. Male ventral right thorax, showing nearly equidistant coxal spacing. 4. Male ventral terminal abdomen. Specimen from French Polynesia, Hiva Oa, Mt. Temetiu, CL 6031.