Alexander, C.P. 1928. New or little-known Tipulidae from eastern Asia (Diptera). II. Philippine Journal of Science 35: 466.
Protohelius is a small genus that is based on the characteristic wing venation of its members. Three branches of Rs attain the wing margin with vein R3 located in the position typically held by R1. Vein R1 is present as a small element located basal to R3. The genus additionally shows most of its members with the terminal maxillary palpomere elongated to a length nearly twice the length of the penultimate segment.
Head: Anterior vertex suppressed, narrowly produced. Rostrum length less than that of the remaining head. Maxillary palpus subequal to longer than remaining head; basal palpomeres subequal, terminal segment subequal or nearly twice penultimate.
Antennae: 14 articles; antennomeres elongate-cylindrical, distal segments decreasing in length.
Wing: Subhyline; stigma present; anal angle present. Wing venation: Sc1 long, removed from Sc2; both elements ending near or after split of Rs; R1+2 in near alignment with R2; free branch of R1 attaining wing margin; three branches of Rs (R3, R4, R5) attaining wing margin; two Medial veins (M1+2, M3) attaining wing margin; cell dm present; anterior wing chord in general alignment in distal 1/2 of wing; two Cubital veins (CuA1, CuA2) attaining wing margin; two Anal veins (A1, A2) attaining wing margin.
Male hypopygium: 9th tergite (9t) and sternite (9s) fused, only slightly divided by a midventral membrane. Mesoventral lobe of gonocoxite absent or reduced. Gonostylus bifid; dorsal style heavily sclerotized, broad based and narrowing to a slender tip, equipped with a short blunt lobe at about 1/3 its length; ventral style less sclerotized than dorsal, broad based, narrowing to a slender tip, equipped with a short fleshy lobe near its base, subequal to dorsal style. Aedeagus cylindrical and strongly produced, its tip with two spinupous points, with a single subterminal opening. Proctriger simple, without modification.
Protohelius is a small genus (7 species) that shows a distinct equatorial distribution. The genus is most strongly represented in the Oriental Region (4 species). The remaining species are divided between the Eastern Paleactic (1 species) and Neotriopical (2 species) Regions.
The larval habitat of this genus is unknown.
