Gracilorrhina, Hippa, Heikki, Mattsson, Ingegerd & Vilkamaa, Pekka, 2005

Hippa, Heikki, Mattsson, Ingegerd & Vilkamaa, Pekka, 2005, New taxa of the Lygistorrhinidae (Diptera: Sciaroidea) and their implications for a phylogenetic analysis of the family, Zootaxa 960, pp. 1-34 : 17-19

Genus Gracilorrhina gen. n.

Type­species Gracilorrhina gracilis sp. n.

Description. Small­sized Lygistorrhinidae , total length about 2.5 mm, wing length about 1.5 mm.

Head. Number of ocelli 2, a rudiment or the site of the median ocellus discernible in a depression in front of vertex. Dichoptic, all facets similar in size. Interommatidial setae slightly longer than diameter of ommatidia. Frons with rows of dorsolateral setae. Prefrons/face non­setose. Clypeus non­setose. Labella about one half of height of head. Palpi about two­thirds as long as labellum, with several low dorsal pits with a hyaline sensillum in each. Hypopharynx about one­third as long as labellum. Antenna about 4 times the height of head. Flagellum with 14 flagellomeres, these laterally flattened and strongly ventrally expanded on their basal two­thirds, in dorsal and ventral view several longer than broad, in lateral view as long as broad, this modification of flagellomeres diminishing towards the apex of flagellum and even rather weak on flagellomere 1, seta­like sensilla on flagellomeres numerous, scattered.

Thorax. Scutum roundedly dome­shaped, anteriorly extending to the same level as base of coxa 1, the setae unevenly distributed with a wide non­setose stripe between medial and lateral setae. Suture between anepisternum and katepisternum incomplete, anteriorly obliterated. Katepisternum unusually high. Pleural pit indistinct. Laterotergite produced lobe­like posteroventrally, with or without setae. Anterior margins of episternum 3 and laterotergite at the same vertical level. Legs. Very long, tibia 1/length of scutum plus scutellum 1.36–1.42. Coxa 1 unusually long, more than 1.5 times length of coxa 3. Coxa 2 conspicuously longer than coxa 3, its apex not reaching apex of coxa 3. Coxa 3 without a basolateral depression, with setae only apically. Femur 1 and 2 slender, approximately equally broad, femur 3 stouter, twice as thick as femur 1. Tibia 1 with two dorsal, two ventral and one pro­ and one retrolateral row of socketed setae of equal size, with trichia of half the length of setae on all sides, in rather distinct rows, with microtrichia through the whole length on all sides, tibial organ subapically on prolateral side not differentiated, dotlike sensilla present in a row on retrolateral surface; spur lacking. Tibia 2 with chaetotaxy, trichiation and sensillar pattern similar to tibia 1; one spur present, 1.5 times apical width of tibia. Tibia 3 club­shaped, greatest width of enlarged apical part 2.5 times the subbasal width of tibia, widened apical part scarcely extending to basal half; whole of hind tibia microtrichose on all sides, a few stripes of trichia on both pro­ and retrolateral sides of the expanded apical part, scattered setae of equal size on all sides of tibia but with a broad non­setose dorsal stripe on both pro­ and retrolateral sides, on the narrow basal half of tibia the setae only in one dorsal, ventral, prolateral and retrolateral stripes, apex without a transverse row of several strong setae on retrolateral side; dot­like sensilla scattered in a stripe on apical half of tibia, coinciding with both pro­ and retrolateral non­setose stripes; two spurs present, the longer retrolateral one about twice, the shorter retrolateral one about 1.5 times, width of tibial apex. Length of basitarsomere 1/length of tibia 1 0.82–0.93, basitarsomere 3 about twice the thickness of basitarsomere 2. Claws of all legs pointed. Wing. Wing length 1.34–1.54 mm. Costa without a swelling at junction with R1. Humeral cross vein weak. Subcosta vestigial, ending free but directed towards R1. R1 short, meeting costa well basal of middle of wing, non­setose. R5 non­setose. M1 slightly curved. M2 sigmoid. Distance between apices of M1 and M2 greater that that between M2 and CuA1. Haltere long, longer than thorax.

Abdomen. Sternite 8 strongly modified, with a posterior process. Gonostylus narrow, nearly 4 times as long as broad, with a long apical tooth, with a long straight subbasal mesial seta. Tegmen with a nose­like ventral protuberance well basad of apical margin. Parameres only slightly curved, almost straight, the apices reaching more posteriorly than the posterior margin of tegmen.

Etymology. The generic name is a combination of the name of the type­species and the last part of the name Lygistorrhina . The name is feminine.

Discussion. In the male characters, Gracilorrhina differs from all other known Lygistorrhinidae by the shape of the antennal flagellomeres, which are unusually ventrally expanded on the basal two­thirds ( Fig. 4 E), giving the flagellum a serrate impression. Only a slight tendency towards a similar modification is seen in the species of Blagorrhina , Labellorrhina quantula , and Lygistorrhinidae sp. 1. Gracilorrhina is similar to Blagorrhina , Loyugesa , Matileola , and Seguyola in having the median ocellus reduced. Gracilorrhina differs from them all by having 14 flagellomeres instead of fewer. Gracilorrhina differs from Blagorrhina by having stCuA present and a non­setose lateral stripe on scutum; from Loyugesa and Matileola by the slender hind basitarsomere, from Loyugesa by being dichoptic; and from Seguyola by lacking a conspicuous colour pattern on wings, by lacking a swelling on the costa at the apex of R1, by having R1 short, in the basal half of the wing instead of extending well into the apical half, and by having a slender, not tumid, hind basitarsomere. See also under Lygistorrhinidae sp. 1 below.

Figures

FIGURE 4. Antennal flagellomere 4, lateral view. A: Blagorrhina blagoderovi sp. n. (paratype). B: Labellorrhina quantula sp. n. (paratype). C: Lygistorrhinidae sp. 1 (Malaysia). D: Blagorrhina brevicornis sp. n. (paratype). E: Gracilorrhina gracilis sp. n. (paratype). F: Labellorrhina grimaldii sp. n. (holotype). Scale 0.05 mm. 1: socketed seta, 2: seta­like sensillum / unsocketed seta, 3: peglike sensillum.