Hesperinus Walker, 1848

Krivosheina, N. P., 2024, FIRST RECORD OF HESPERINUS CUSPIDISTYLUS HARDY ET TAKAHASHI, 1960 (DIPTERA: HESPERINIDAE) FROM RUSSIA, Far Eastern Entomologist 502, pp. 8-11 : 9-10

Genus Hesperinus Walker, 1848

Type species: Hesperinus brevifrons Walker, 1848 .

DIAGNOSIS. Species of the genus have a fragile, narrow body with elongated, thin legs. The male's body is black, with round dichoptic eyes. The wing is wide, transparent, with a slight smoky tint, the subcostal vein is long, flows into the costal vein behind the middle of the wing, the costal vein reaches the apex of the wing, slightly protrudes beyond the point of connection of the costa with the radial vein, the radial veins are branched, R 4+5 is strongly arcuate in apical half. The species are characterized by a peculiar form of antennae, different from those of all nematocerous dipterans. The antennae are elongated, in the male they are longer than the head and thorax combined. The antennal flagella are narrow, almost cylindrical, but rounded at the apex, and consist of 10 segments. The first segment is long, it is at least 2 times as long as the head, the 2nd–5th segments are almost equal in length and slightly exceed half the length of the first, the 1st–5th segments have a characteristic angular apical protrusion of different sizes. The abdomen is long and narrow, with massive broad genitalia.

Males of Hesperinus are characterized by massive, voluminous genitalia, much larger in comparison with the narrow long segments of the abdomen, genitalia are of various shapes and in general bear little resemblance to similar structures in representatives of other families of nematocerous dipterans. The shape of individual structures appears differently depending on the viewing angle. Genitalia with well-developed lamellar tergite 9 and sternite 9, somewhat elongated gonocoxites and large gonostyli of a peculiar shape (massive, elongated oval or lamellar). The most similar in structure are the internal structures (parameres, gonocoxites and apodemes of the aedeagus).

COMPOSITION. The six species have been recorded in the Palaearctic: H. cuspidistylus Hardy et Takahashi, 1960 , H. graecus Papp, 2010 , H. imbecillus (Loew, 1858) , H. nigratus Okada, 1934 , H. ninae Papp et Krivosheina, 2009 , and H. rohdendorfi Krivosheina et Mamaev, 1967 . Two species are known from the Western Hemisphere: H. brevifrons Walker, 1848 from North America and H. conjungens Schiner, 1868 from Brazil. The first species, H. brevifrons , was described and recorded based on materials from Alaska and the USA (Colorado, Utah, British Columbia, Ontario), as well as from Canada ( Hardy & Takahashi, 1960; Krivosheina & Mamaev, 1986; Hardy, 1966; Papp & Krivosheina, 2009; Papp, 2010).

REMARKS. Larvae of H. rohdendorfi develop in the thickness of dead rotting wood of various deciduous species: elm, maakia, chosenia, alder, aspen, and birch. The larvae are most common in elm, chozenia and alder stumps, in fallen alder branches lying on the soil surface, in damp birch trunks lying on the ground (Primorsky Krai: Ussuriysky and Kedrovaya Pad Nature reserves). Larvae are usually not found under the bark. The larvae develop in relatively dense wood of different types of decay, affected by light and blackened rot, but are absent in brown rot. In large logs and stumps, the larvae are concentrated in peripheral areas, and small trunks colonize along the entire diameter, making longitudinal passages, usually forming colonies of up to several dozen specimens. In some biotopes, larvae reach such high numbers that they become an important factor in the process of natural destruction of wood. Adult larvae overwinter and move to the surface layers of the substrate before pupation ( Krivosheina & Mamaev, 1967) .

Larvae of H. ninae inhabit brown fragile wood of fallen Fagus orientalis where they were discovered at the periphery of the trunk together with the larvae of Symmerus annulatus (Meigen, 1830) ( Ditomyiidae ) ( Krivosheina & Krivosheina, 2015).