Cryptostemma Herrich-Schaeffer, 1835

Yamada, Kazutaka & Hayashi, Masami, 2019, Two new species of the genus Cryptostemma from Japan (Hemiptera: Heteroptera: Dipsocoridae), Acta Entomologica Musei Nationalis Pragae 59 (2), pp. 381-390 : 382

Cryptostemma Herrich-Schaeffer, 1835

Diagnosis. HEISS & PÉRICART (2007) provided the following diagnostic characters to distinguish Cryptostemma from the other two known genera of Dipsocoridae , Alpagut and Pachycoleus : left laterotergite VI transformed as appendage of genital complex; left and right laterotergites VIII appendage-like, articulated, and prehensile; parameres asymmetrical; seminal capsule subspherical, not fixed by surrounding cuticules, loculus capsulae lacking.

Discussion. Cryptostemma is more species-rich than the other two genera and currently composed of approximately 20 recent species from all zoogeographical regions ( WYGODZINSKY 1950, 1952, 1955; HILL 1987; LINNAVUORI 1974; ŠTYS 1977; KERZHNER 1995; HEISS & PÉRICART 2007; AUKEMA et al. 2013; WEIRAUCH & FERNANDEZ 2015) and one fossil species from Eocene amber of France ( HARTUNG et al. 2017). Of the extant species, nine are known from the Neotropical Region, six from the Palaearctic Region, and five from the Australian Region (e.g., HILL 1987, KERZHNER 1995, WEIRAUCH & FERNANDEZ 2015). The genus is also present in the Ethiopian Region ( Sudan, Madagascar) and North America ( LINNAVUORI 1974, ŠTYS 1977). In the East Palaearctic Region, four species, including the two new species described below, are recognized: C. digitum Wu, 1967 (Taiwan) , C. wygodzinskyi Wu, 1967 (Taiwan) , C. miyamotoi sp. nov. ( Japan), and C. pavelstysi sp. nov. ( Japan).

Previous authors provided generic diagnoses (e.g., REUTER 1891, MCATEE & MALLOCH 1925, WYGODZINSKY 1948, LINNAVUORI 1951, JOSIFOV 1967), but this genus is still not defined by consistent diagnostic characters. HEISS & PÉRICART (2007) provided the structures of male abdominal appendages and parameres and female genitalia as diagnostic characters for recognizing three dipsocorid genera, but their keys are generally restricted to the western Eurasian species. Eventually a world revision would be required to redefine Cryptostemma .

Through examination of the Taiwanese C. digitum specimens and the two Japanese species, it was revealed that these species share characteristic features, such as the dextrally curved pregenital abdomen, left sternite VII shaped as an appendage-like structure, and extremely enlarged right laterotergite VIII. WU (1967) described that C. digitum has appendage-like left laterotergite VI. Based on our careful examination of C. digitum specimens, this character was proven to be sternite VII, not laterotergite VI.

Judging from the illustration of C. wygodzinskyi by WU (1967), it was recognized that the species also has appendage-like left laterotergite VII, so Wu seems to have misidentified laterotergite VII for VI. As did WU (1967), JOSIFOV (1967) also misidentified the laterotergite VII for VI, and subsequent authors who followed them might have done the same. The past authors might have wrongly interpreted homology of the sclerites; therefore, comparative morphological studies on male abdomen are indispensable to evaluate their homology carefully.