Microphorella acroptera species group

Diagnosis. The Microphorella acroptera species group can be distinguished from other Nearctic Microphorella species groups by the following suite of characters: clypeus separated from face by suture (except in M. maculata sp. nov.); mouthparts with sensory pit on palpus (sometimes difficult to see in non-macerated specimens); male hind trochanter with tubercle bearing spine-like seta (Figs 8, 9, 18, 21, 24, 48, 51, 66, 73, 77, 93, 94; very small in M. maculata sp. nov.); male hind femur without patch of fine setae on posterior surface; wing with moderately long R 1 vein that usually terminates beyond midpoint of wing (Figs 4, 17, 47, 88, 89, close to midpoint of wing in some specimens, Fig. 95); male abdominal sternite 5 with broad ventral projection (Figs 10, 46, 49–51, 66, 70); hypopygium (Figs 11–14, 25–31, 36–40, 41–45, 52–55, 67–69, 78–85, 90, 91, 97–99) with ventral edge of epandrium fused to hypandrium, but with margin mostly defined (margin partially indistinguishable in M. maculata sp. nov.); right epandrial lamella without ventral epandrial process; hypandrium bare; female abdomen (not known for M. convoluta sp. nov., M. maculata sp. nov., M. subacroptera sp. nov. and M. trochanterata sp. nov.) with tergite 5 usually bearing a cluster of stout medial setae (Fig. 20), tergite 6 with setae on posterior margin unmodified (i.e., not forming prominent row of long, stout setae), syntergite 9+10 with acanthophorous spines and cercus narrow and pointed.

Distribution. The M. acroptera species group is known to occur from southeastern Alberta and northeastern Montana south to Washington, western Oregon and southern California, east to southwestern Nevada and northwestern Arizona (Figs 100–105). The majority of records are from California.

Remarks. The M. acroptera species group is a morphologically heterogeneous assemblage but is considered to be monophyletic based on the possession of a tubercle on the hind trochanter of males (Cumming & Brooks 2019). The species group comprises four distinct lineages, which are characterized below. Members of this species group are rarely collected, particularly in long series and are relatively scarce in collections. Adults have been taken in various riparian habitats, from moist temperate rainforests to desert oasis habitats (Figs 1–3).

Included species. This group includes the following 16 described species: M. acroptera Melander, M. acuminata sp. nov., M. bifida sp. nov., M. compacta sp. nov., M. convoluta sp. nov., M. cornuta sp. nov., M. elongata sp. nov., M. maculata sp. nov., M. paracroptera sp. nov., M. serpentina sp. nov., M. sinuosa sp. nov., M. subacroptera sp. nov., M. tenuis sp. nov., M. triangulata sp. nov., M. trochanterata sp. nov. and M. tubifera Melander. One additional species is known ( Microphorella sp. A, see below), but is not formally named and described on account of the poor condition of the unique male specimen.