Hypseloecus Reuter, 1891

Hypseloecus Reuter, 1891 View in CoL View at ENA

Diagnosis: This unique genus is readily separated from other pilophorines by the following distinctive characters: body rounded or ovoid, tortoise-shaped, stout ( Fig. 1A, C, F View FIGURE 1 ), with densely distributed, silvery, lanceolate, scale-like setae (which are very easily rubbed off, cf. Fig. 1E View FIGURE 1 vs. 1F); basic coloration variable, usually brown, reddish brown or fuscous (exceptionally yellowish or pale olive as in H. articulates Yeshwanth, 2014 from India and H. fukutomii sp. nov., Fig. 2A View FIGURE 2 ); head short and wide, wider than high in frontal view ( Figs. 1B View FIGURE 1 , 6D, H–I View FIGURE 6 ); dorsal surface usually with dark, simple setae mixed with silvery scale-like setae ( Fig. 6A–B View FIGURE 6 ); antenna generally linear and long, with segment II not thickened towards apex; mesepimeron and episternum each with a fuscous ocellate spot ( Fig. 1C, F View FIGURE 1 ) which are composed of dense microstructure or villi (anterior and posterior pleural glands, sensu Yasunaga & Duwal 2019, cf. Fig. 6B, E, N, P View FIGURE 6 ); hemelytra strongly declivous at cuneal fracture ( Fig. 1C, F View FIGURE 1 ); vesica typical pilophorine in form, with one or two median processes ( Fig. 3D, H View FIGURE 3 ); sclerotized rings thick-rimmed, usually with toughened anterior margin ( Fig. 4B, F View FIGURE 4 ); vestibular sclerite well-developed ( Fig. 4C View FIGURE 4 ). Further diagnostic characters and morphology were discussed by Schuh & Menard (2011), Yasunaga et al. (2015) and Yasunaga & Duwal (2019).

Discussion. Although many members of Pilophorini are considered zoophytophagous (Yasunaga et al. 2021; Noguchi et al. 2023), most (or possibly all) of Hypseloecus congeners preferably inhabit and feed on the hemiparasitic Loranthaceae and Santalaceae mistletoes ( Schuh & Menard 2011; Yeshwanth 2014; Yasunaga et al. 2015; Yasunaga & Duwal 2019). In Japan, Hypseloecus nakagawai Yasunaga & Duwal, 2019 ( Fig. 2F–G View FIGURE 2 ) is known to be associated only with Viscum album L. ( Santalaceae ), whereas the two new species described below were found from Taxillus hosts ( Loranthaceae , Fig. 1D View FIGURE 1 ). The breeding host of H. takahashii Yasunaga, 2001 ( Fig. 1G View FIGURE 1 ) is yet to be confirmed.

Since the mistletoes are zoochorous and the dispersal is depend principally on frugivorous birds, the plant communities are usually scattered on restricted tree canopies. Yasunaga & Duwal (2019) hypothesized that Hypseloecus species may utilize certain chemical signals for intraspecific communication (such as an aggregation pheromone). The unique structures, anterior and posterior pleural glands, possessed by Hypseloecus members are presumed to function as the secretion organ of potential pheromones, which requires further biochemical verification.