Charismatic Hypselosomatinae (currently 14 extant and fossil genera; 72 species), the “big-eyed minute litter bugs”, are characterized among Schizopteridae (Dipsocoromorpha) by the large eyes, four-segmented labium, and distinctive wing venation. A recent molecular phylogenetic analysis confirmed the monophyly of Hypselosomatinae that were recovered as the sister taxon to the Ogeriinae + Schizopterinae (Weirauch and Štys 2014). Hypselosomatinae occur in the Old and New Worlds, but described species diversity is biased towards the Oriental and Australian regions: only three monotypic genera are currently known from the New World (Glyptocombus Heidemann, Ommatides Uhler, and Williamsocoris Carpintero & Dellapé). Based on 28 male, female, and juvenile specimens from Cuba and the Dominican Republic and a single male specimen from Brazil we here describe two new monotypic genera of Hypselosomatinae, Hypselosomops pecki gen. n. and sp. n., and Hypsohapsis takiyae gen. n. and sp. n. We provide habitus images, digital illustrations (light, scanning electron, and/or confocal microscope) of wing and male genitalic structures, line drawings of genitalic structures, and distribution maps. Bizarre morphologies, a worldwide distribution with small endemic species ranges, and a fossil record that dates back to the mid-Cretaceous make the Hypselosomatinae a fascinating group to explore in an effort to understand the evolutionary history of Dipsocoromorpha.

Dipsocoromorpha , taxonomy, morphology, Neotropics, Hypselosomops pecki , Hypsohapsis takiyae

Schizopteridae are tiny (1–3 mm) yet charismatic Heteroptera, the study of which is hampered by their cryptic habits and small size that make them rare in collections and difficult to examine. Adults display extreme wing polymorphism ranging from apterous to macropterous and elytrous, with the latter being a wing type that is very rare outside of Coleoptera. Wing polymorphism can be sexually dimorphic (Wygodzinsky 1948, Emsley 1969, Hill 2013, Knyshov et al. 2016, Leon and Weirauch 2016), but may also occur amongst individuals of the same sex (Hill 1980; Alexander Knyshov, pers. obs.). In addition, extreme asymmetry of the male genitalia, a feature that is fairly rare in Heteroptera, is widespread in Schizopteridae and often includes modifications of the pre-genital abdomen (Emsley 1969, Štys 1970). With 72 described species, the subfamily Hypselosomatinae, also known as “big-eyed minute litter bugs”, is currently the second largest subfamily of Schizopteridae. Diagnostic features include the very large eyes, often overlapping the margins of the prothorax, four-segmented labium, well developed ovipositor, and distinctive wing venation of four closed marginal cells after the costal cell (Emsley 1969, Lionel Hill 1980). Hill (1980) in addition discussed the following characters as potentially diagnostic for the subfamily: anterior sclerites formed from the ninth abdominal segment and forming part of the ovipositor (referred to by Hill (1980) as gonangulum struts) fused to ninth segment; three, six or seven pairs of abdominal spiracles; hind wing, when present, with jugal lobe; and possession of gonoplacs in females. Emsley (1969) recognized Hypselosomatinae as a well-defined group in his schema of proposed relationships among Schizopteridae, and the only published phylogenetic analysis confirmed the monophyly of this group with high branch support, although only four of the currently recognized 14 genera were represented in that analysis (Weirauch and Štys 2014).

The taxonomic history of this group started in the late 19^th century with the almost simultaneous description of Old World Hypselosoma oculata Reuter by Reuter (1894) and New World Ommatides insignis Uhler by Uhler (1894). A second New World genus, Glyptocombus Heidemann, was described after the turn of the century (Heidemann 1906) and various scientists added species to the Old World genus Hypselosoma Reuter: Horvath (1905) [1 species], Esaki and Miyamoto (1959) [1 species], McAtee and Malloch (1925) [1 species], and Wygodzinsky (1960) [9 species]. Much later, the hypselosomatine diversity of Australia and adjacent regions was extensively studied by the most prolific taxonomist to focus on this subfamily, Hill, who has described 7 new genera and 53 new species during the past 25 years (Pateena Hill, Macromannus Hill, Ordirete Hill, Lativena Hill, Cryptomannus Hill, Duonota Hill, Rectilamina Hill (Hill 1980, 1984, 1985a, 1985b, 1987, 1991). The third New World genus, Williamsocoris Carpintero and Dellapé, was recently described from Argentina (Carpintero and Dellapé 2006). Together with three monotypic genera that are based on fossils, Libanohypselosoma Azar and Nel, Buzinia Perrichot, Nel and Néraudeau, and Tanaia Perrichot, Nel and Néraudeau (Azar and Nel 2010, Perrichot et al. 2007), 72 species in 14 genera are currently recognized in the Hypselosomatinae.

The Hypselosomatinae have a worldwide distribution but are most diverse in the tropics, a pattern similar to those observed in other groups of Dipsocoromorpha. The greatest described diversity is from the Indo–Pacific and Australia, but this may be an artifact due to Hill’s focus on that biogeographic region and the lack of research on the Oriental, Afrotropical, and Neotropical regions. Hypselosomatines inhabit cryptic and typically moist microhabitats such as leaf litter, low vegetation, the interstitial zone of streams, and even mangroves (McAtee and Malloch 1925, Emsley 1969, Hill 1984, 1991, Melber and Köhler 1992, Schuh and Slater 1995, Ng et al. 1999). Published distributional data are scarce for Hypselosomatinae beyond the well-documented Indo–Pacific and Australian fauna. Despite the fact that Hill (1984) suspected that new taxa of hypselosomatines are unlikely to be discovered in South America, the recently described Williamsocoris was collected in Argentina. Along similar lines, Wygodzinsky (1960) commented on the absence of Hypselosomatinae in Africa despite their presence in Madagascar. Based on examination of schizopterid specimens that we have assembled from various natural history collections and that include ~632 specimens of Hypselosomatinae, we have discovered a number of undescribed Hypselosomatinae from Central and South America, Africa, and the Indo–Pacific region. In the New World, we have examined Hypselosomatinae from Panama, Suriname, Ecuador, Peru, Dominican Republic, Costa Rica, Mexico, USA [FL, GA, TX, OK, AR, KS, TN, MD, MI], Trinidad and Tobago, French Guiana, Colombia, Cuba, and Brazil (Fig. 1). This publication focuses on a subset of these specimens, specifically specimens from Cuba, the Dominican Republic, and Brazil that represent two new monotypic genera that we here describe and document using light, scanning electron, and confocal microscopy. Future publications will focus on the remaining specimens from other localities that are likely new species of already described genera.

Figure 1. 

Map of distribution of all New World Hypselosomatinae (generated using data entered in the American Museum of Natural History’s Arthropod Easy Capture Software database (http://www.research.amnh.org/pbi/locality/index.php))

Based on our extensive specimen sorting efforts of Dipsocoromorpha with emphasis on Schizopteridae as part of the NSF-funded ARTS Litter Bug project, it has become clear that Hypselosomatinae are more widely distributed in the New World than previously documented and that a number of undescribed species remain to be described. The present contribution focuses on two new genus-level taxa, but descriptions of additional species are in progress and the analysis of molecular data will provide a phylogenetic framework for both New and Old World Hypselosomatinae (Hoey-Chamberlain and Weirauch, in prep.). The three previously described New World genera share a number of morphological characters. Ommatides and Williamsocoris both possess dorsally expanded first labial segments, while the male genitalia in Williamsocoris and Glyptocombus are very similar, both with a fingerlike process apically on sternite nine. The males of both Ommatides and Glyptocombus are submacropterous and elytrous. We have not been able to recover additional specimens of Ommatides insignis beyond the male holotype and certain details of the male genitalia therefore remain unknown. We were also unable to locate specimens that Wygodzinsky (1960) suspected to represent an undescribed species of Glyptocombus from southeastern Brazil, but for which he did not indicate the depository. Finally, we have discovered female hypselosomatine specimens that derive from the same collection events as males of Williamsocoris and Glyptocombus and we suspect that they represent conspecific females. These females lack the dorsally expanded first labial segment making genus-level identification of unassociated females impossible. We suspect that a more thorough study of described and undescribed species of Williamsocoris and Glyptocombus may lead to the conclusion that the two genera are synonyms. In contrast, the two new genera that we describe here are significantly different from the previously described genera, despite the fact that Hypselosomops possesses a slightly expanded first labial segment similar to Ommatides and Williamsocoris, and Hypsohapsis, Ommatides, and Glyptocombus share the elytrous condition of the hemelytron.

In a series of taxonomic publications focusing on Hypselosomatinae, Hill (1980, 1984, 1985, 1987, 1991, 2013) established a set of characters that are useful for distinguishing genera, including the number of macrosetae on the clypeus, tarsal formula, wing venation and number of marginal cells beyond the costal cell, and the presence/absence or degree of sclerotization and shape of the spermatheca. In the following, we discuss some of these diagnostic features in the context of the two newly discovered and described New World genera. Hypsohapsis shares the presence of five macrosetae on the clypeus with Hypselosoma, while females of Hypselosomops share three macrosetae with the previously described New World genera, the fossil taxa, and four of the Old World genera (Pateena, Duonota, Ordirete, and Macromannus) and males lack clypeal macrosetae similar to the Old World genus Rectilamina. Among New World genera, the tarsal formula of the males of Glyptocombus and Williamsocoris is 3-3-3, but it is 2-2-3 in the female of Glyptocombus; in contrast, the male of Hypselosomps has a tarsal formula of 2-3-3, while the formula of the female is 2-2-3. The tarsal formula of Ommatides is unknown (most legs and all tarsi missing in the holotype and single known specimen). Sexual dimorphism in the tarsal formula is fairly common across Schizopteridae (Emsley 1969).

Even though a diagnostic feature of Hypselosomatinae, the default number of four marginal cells can be modified, especially in micropterous and elytrous taxa. Four marginal cells are clearly visible in most macropterous taxa such as Williamsocoris and the male, macropterous form of Hypselosomops, but Glyptocombus, Ommatides, and Hypsohapsis have reticulate wings and/or reduced wing venation. Wing type in Hypselosomatinae can vary within species, but even within the same sex of the same species. Sexual dimorphism with respect to wing type occurs in taxa in both the Old (e.g., Rectilamina, Duonota, and Hypselosoma) and New Worlds (undescribed species of Williamsocoris and Glyptocombus; pers. obs.). Only Hypselosomops pecki and Pateena elimata Hill (Hill 1980) are currently known to comprise both micropterous and submacropterous wing types in the male.

Carpintero and Dellapé (2006) reported the pronotal collar to be absent in Williamsocoris. We argue that the structure indicated by arrow F in Figure 12 represents the collar; a collar is also present in specimens that we have discovered through our sorting efforts and that likely represent undescribed species of Williamsocoris. Hill (2013) mentions that in the Old World genus Cryptomannus the pronotal disc overlaps the collar. A similar situation in Williamsocoris before clearing and slide mounting could have resulted in this misinterpretation.

Figure 12. 

Ommatides insignis holotype: A enlarged first labial segment B anterior teeth like setae; Williamsocoris ornatus holotype: C enlarged first labial segment D horn like or tubular structure occupying third and fourth labial segments E anterior teeth like setae of first labial segment F pronotal collar G projection of genital capsule; and Glyptocombus saltator non-type: H projection of genital capsule

Although considered to be of value as a diagnostic feature at the genus level, comparative documentation of the spermatheca across Hypselosomatinae is rather incomplete. Females of Williamsocoris, Glyptocombus, Ommatides, and Hypsohapsis remain unknown and the spermatheca is assumed to be absent or poorly sclerotized in Hypselosoma (Hill 1980, 2013). In the few taxa for which the spermatheca has been documented, namely Rectilamina (Hill 1980), Duonota (Hill 1984) and Hypselosomops it is well-sclerotized and pigmented, with a well-defined spermathecal gland, gland duct, reservoir, and duct.

The number of abdominal spiracles can vary dramatically between hypselosomatine genera, although variation can also occur within a genus. Hill (2013) confirmed three abdominal spiracles in species of Hypselosoma from Australia, New Zealand and New Caledonia, while Esaki and Miyamoto (1959) reported that the first five spiracles are reduced in H. hirashimai Esaki & Miyamoto from Japan, resulting in only three pairs of spiracles. Species of Pateena can have five or six (Hill 2013) or even seven abdominal spiracles (on segments two through eight) (Hill 1980). Hill (1980) found six spiracles (on segments two through seven) on a specimen of Glyptocombus sp. that Allen and Carlton (1989) later suspected to be G. saltator Heidemann. Hypselosomops has two pairs of abdominal spiracles, Hypsohapsis seven pairs, but the condition remains unknown in Williamsocoris. Given that spiracle numbers and arrangement are variable within a genus, this character should probably not used as a diagnostic feature at the genus level unless studied in a broader sample of species.

Phylogenetic hypotheses are currently unavailable for Hypselosomatinae and our understanding of character evolution in the group is therefore limited to speculations. Hypsohapsis shares a number of morphological features with Macromannus and Ordirete including the three clypeal macrosetae, elytrous wings with reticulate/areolate pattern and the simple sternite nine with a rounded lobe. Hypselosomops in contrast more closely resembles Duonota and Rectilamina due to the lack of clypeal macrosetae on males and the three clypeal macrosetae on females, as well as, the modifications of tergite eight in males and the presence and shape of the spermatheca in females. Given some of the extraordinary morphologies of Hypselosomatinae, the worldwide distribution with small endemic species ranges, and the fossil record that dates back to more than 100 my (Perrichot et al. 2007, Azar and Nel 2010), a phylogenetic hypothesis for the group is long overdue and will also allow for ancestral state reconstructions of morphological characters that will improve our understanding of the evolutionary history of this charismatic taxon.

We thank curators, collection managers, and research staff at various institutions for their help in facilitating specimen sorting and loans: James Boone, Rebekah Baquiran, and Margaret Thayer (FMNH); Edward Riley (TAMU); and Daniela Takiya (UFRJ). Robin Delapena (FMNH) did a wonderful job in sorting hundreds of bulk samples and recovering many of the specimens used in this study. We thank the Heteropteran Systematics Lab graduate students Eric Gordon, Alexander Knyshov, Sarah Frankenberg, and Paul Masonick for their constructive criticism and feedback on the manuscript. We are grateful to Serguei Triapitsyn and Vladimir Berezovskiy (UCR) for training and help with permanent slide-mounting of specimens and István Mikó (Penn State) for advice on confocal microscopy. This project is part of the “ARTS: Litter Bugs: revisionary and phylogenetic research on the least studied true bug infraorder (Insecta: Hemiptera: Dipsocoromorpha)” project (DEB-1257702) supported by the US National Science Foundation.