Labellorrhina, 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 : 12-13

Labellorrhina gen. n.

Type­species Labellorrhina quantula sp. n.

Description. Small­sized Lygistorrhinidae , total length about 1.5 mm, wing length about 1 mm.

Head. Number of ocelli 3. Compound eyes dichoptic, the facets becoming larger laterally and dorsally. Interommatidial setae as long as the facets. Frons without dorsolateral setae. Prefrons/face non­setose. Clypeus setose. Labella as long as or slightly shorter than height of head. Palpi one­half to three­fourths of the length of labella, apically pointed, with several low dorsal pits with a hyaline sensillum in each. Hypopharynx slightly shorter than labella. Length of antenna about 1.5 times the height of head. Flagellum with 14 flagellomeres, these from as long as broad to shorter than broad, not expanded on ventral half, with the longer seta­like sensilla in one whorl.

Thorax. Scutum roundedly dome­shaped, extending more anteriorly than base of coxa 1, wholly setose. Suture between anepisternum and katepisternum complete, extending to anterior margin of the sclerites. Pleural pit indistinct. Laterotergite produced lobe­like posteroventrally, setose. Anterior margins of episternum 3 and laterotergite at the same vertical level. Legs. Long, length of basitarsomere 1/length of scutum + scutellum 0.89–1.07. Coxa 2 longer than coxa 3, its apex not reaching the apex of coxa 3. Coxa 3 without a basolateral depression, with only a few setae. Femur 1 and 2 slender, femur 1 a little broader than femur 2, femur 3 about twice as broad as femur 1, or femur 1 and 2 distinctly thickened but less than femur 3 which is 1.5 times as broad as femur 1. Tibia 1 socketed setae placed in several dorsal and ventral stripes and in a medial stripe on both lateral sides, all subequal in size, non­socketed setae/trichia half as long as socketed setae, in several distinct stripes through the whole length and on all sides, microtrichia absent except at extreme base, dot­like sensilla present as a medial row on distal half of retrolateral side; tibial organ absent; the spur present. Tibia 2 similar to tibia 1; two spurs present, the prolateral one shorter than the retrolateral one. Tibia 3 club­shaped, the greatest width of enlarged apical part a little more than twice the subbasal width of tibia, expansion of apical part beginning well in basal half of tibia, microtrichia absent except at extreme base, dotlike sensilla in a scattered laterodorsal stripe on apical third of the retrolateral side, nonsocketed setae/trichia over whole tibia in more or less distinct stripes, pattern of socketed setae similar to that on tibia 1 and 2 but the dorsal retrolateral setae conspicuously stronger than other setae, and with a transverse subapical retrolateral row of many strong dark setae; two spurs present, the longer retrolateral one twice the apical width of tibia, the shorter prolateral one half of that. Basitarsomere 3 slender, about twice as broad as basitarsus 1. Length of basitarsomere 1/length of tibia 1 0.53–65. Claws of legs 1 and 2 blunt, those of leg 3 pointed. Wing. Costa without a swelling at junction with R1. H absent. Sc ending free or wholly absent, in the former case curved towards R1. R1 very short, meeting C at its basal fifth, setose. R5 non­setose. M1 and M2 straight. Distance between apices of M1 and M2 smaller than distance between M2 and CuA1. CuA1 and CuA2 separate. Anal lobe not prominent. Haltere shorter than thorax.

Abdomen. Sternum 8 without a posterior process. Gonostylus narrow, about 4 times as long as broad, with a long apical tooth, with a long curved subbasal mesial seta. Parameres weak, curved, their apices not reaching beyond apical margin of tegmen.

Etymology. The generic name is a combination of the word “labellum” and the last part of the name Lygistorrhina . The name is feminine.

Discussion. With a wing length of approximately 1 mm, Labellorrhina species are the smallest Lygistorrhinidae known. They are combined with Gracilorrhina , Blagorrhina , Loyugesa , Matileola , and Seguyola , and are distinguished from other Lygistorrhinidae by the strongly club­shaped hind tibia, and from all except Seguyola by a short R1 which ends at the costa well within the basal half of the wing. Labellorrhina is distinguished from all of these by having three ocelli instead of two, by having a transverse retrolateral row of strong setae subapically on the hind tibia, and by the characteristic wing pattern with the two dark patches in an otherwise clear wing. Labellorrhina is similar to Gracilorrhina and Matileola in having a plesiomorphous 14­segmented antennal flagellum instead of having a smaller number of segments.