Prohydrometra gagnei (J. Polhemus & D. Polhemus, 1995) J. Polhemus & 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 : 88-90

Prohydrometra gagnei (J. Polhemus & D. Polhemus, 1995) new combination

Figs. 9, 10 , 19, 20 , 27–29

Hydrometra gagnei J. Polhemus & D. Polhemus, 1995a: 2 .

Apterous male. Length 6.80, width 0.50.

Color. Ground color brown to blackish-brown; abdominal mediotergites light-brown medially, matte. Head heavily tinged with blackish except at base. Thorax anteriorly and medially light colored dorsally; each laterotergite with light area anteriorly. Venter of thorax and abdomen dark-brown. Legs light-brown, antennae light-brown to brown; coxae and trochanters mostly light-brown.

Structure. Very similar to the female previously described, except somewhat narrower, and with abdominal sternum VII modified. Acetabula lacking pits. Venter without black denticles.

Proportions of legs similar to the female previously described. All legs with bristly setae, including on coxae, longer basally, but distally with setae about as long as width of segment; setae more pronounced in male than in female.

First abdominal segment short, transverse, clearly delineated by a suture posteriorly. Mediotergites longer than wide. Mediotergites VII and VII thickly set with moderate length semi-erect setae; abdominal sternum VII with two large, erect curved spines, set close together, arising near the anterior margin ( Figs. 19, 20 ); segment VIII cylindrical, unmodified, without distal process.

Material examined (all micropterous). SOCIETY ISLANDS, Tahiti: 1 male, Tahiti Nui , Mt. Marau summit , 1400 m, 20 September 1977, J. Gourves (holotype, BPBM); 2 females, Tahiti Nui , Mt Marau, fern gulley along road to summit , 1380 m, 17°36'28"S, 149°32'09"W, 10 September 2006, CL 7498, D. A. Polhemus ( USNM); 3 males, 8 females, same data as preceding, 2 September 2007, CL 7498, D. A. Polhemus and J. T. Polhemus ( BPBM, USNM); 6 males, 7 females, Tahiti Nui , Mt. Mauru , trail to summit between Pylon 3 and Pylon 4 , 1030 m, 17°38'04"S, 149°22'04"W, 6 September 2006, 13:30–15:00 hrs., CL 7486, D. A. Polhemus ( BPBM, USNM); 3 males, 5 females, same locality and date as preceding but J. K. Liebherr ( CUIC) .

Distribution. French Polynesia, Society Islands, endemic to the island of Tahiti, on Tahiti Nui ( Fig. 29 ).

Discussion. Prohydrometra gagnei may be recognized among its congeners by the pair of large, posteriorlycurved, sclerotized processes on male abdominal venrtite VII, which arise near the anterior margin of the segment and are set moderately close together. This character state is similar to that seen in P. moorea , but in that species the processes are somewhat removed from the anterior margin of the ventrite, and set further apart (compare Figs. 19–21 ).

Certain specimens of P. gagnei from Mt. Mauru, in eastern Tahiti Nui, exhibit an atypical yellowish-brown coloration ( Fig. 20 ). At first it was thought that these might represent a different species, but because they are morphologically similar to the other specimens in hand, it is concluded that this color morph simply represents a degree of intraspecific variation.

Ecological notes. Our knowledge of the habits of P. gagnei is based primarily on many hours of intensive collecting activity on Mt. Marau, a summit above Papeete which can be reached by a road to a radio tower, and indicates that the species is similar in its habitat preferences to the species occupying Mt. Tohiea on Moorea. The majority of the captures have come by fogging vertical exposures of dry Dicranopteris fern fronds along the margins of headwater gulches or upland trails ( Fig. 27 ). Only two specimens have been taken by beating, and both of these were obtained by pushing a net deep inside Dicranopteris fern banks so that it penetrated the dry fronds of the interior, then beating on the overlying fern mass. This apparent preference for masses of dry Dicranopteris fronds is also shared by certain micropterous Nabis species ( N. tahitiensis D. Polhemus, 2010 , N. orohena D. Polhemus, 2010 , N. tangaroa D. Polhemus, 2010 , N. tiki D. Polhemus, 2010 ) with which P. gagnei is frequently syntopic.

An additional series of P. gagnei was taken from Dicranopteris fern banks on Mt. Mauru, a very wet mountain lying in the eastern section of Tahiti Iti. The habits of the species at this locality were very similar to those observed at Mt. Marau above Papeete, with the specimens being obtained by fogging dense fern banks along the trail ( Fig. 28 ).

The captures of P. gagnei at the type-locality on Mt. Marau have consisted largely of females, and it was only after a fourth visit to the summit area of Mt. Marau in 2007 that the males of the species were finally obtained there. The capture ratio of sexes to date at this site has been approximately six females to one male. By contrast, other collections of this species on Mt. Mauru, further to the east, have produced roughly similar numbers of males and females. It is not clear if males of P. gagnei at Mt. Marau live in slightly different microhabitats that make them less amenable than females to collection by fogging and beating, the two primary methods used to date.

Figures

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 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 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 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.