Thereotricha agapa, BLAGODEROV & GRIMALDI, 2004

BLAGODEROV, VLADIMIR & GRIMALDI, DAVID, 2004, Fossil Sciaroidea (Diptera) in Cretaceous Ambers, Exclusive of Cecidomyiidae, Sciaridae, and Keroplatidae, American Museum Novitates 3433 (1), pp. 1-76 : 10-12

? Thereotricha agapa , new species

Figures 5, 6 , Plate 1C

DIAGNOSIS: Three ocelli, touching. Wing membrane with scattered macrotrichia. RS base transverse, shorter than r­m. M 2 probably absent.

DESCRIPTION: Body length = 1.56 mm (rest, estimated length 1.87 mm); wing length 1.48 mm. Partly preserved specimen. Head: Occiput and vertex with straight and curved setae. Three ocelli present, each on its own mound, the latter fused by contacting edges. Eyes bare, with incomplete bridge, deeply emarginate at antennal base. Frontal furrow and keels well developed. Scape and pedicel as long as flagellomeres. Flagellum 14­segmented, flagellomeres barrel­shaped, length about 1.5Χ the width, with few strong setae and numerous fine trichia. Clypeus setose. Palpi 4­segmented, short. Antepenultimate palpomere with dosomedial round sensory pit. Thorax: Proepisternum with 3 long and and 11 shorter setae. Proepimeron touches episternum at the episternal suture, katepisternum with shallow excavation below the point. Anepisternum less than katepisternum, the latter with several trichia in lower part. Laterotergite bare, divided with katepisternum by anepimeron. Mediotergite bare. Metepisternum setose. Scutum with scattered setae. Scutellum with 6 long setae. Wing membrane with microtrichia and macrotrichia mostly in apical and hind area. Costa, R 1, and R 5 with long setae. Sc very short, ends free. R 1 and R 5 almost straight. RS base short, ~0.5Χ r­m length, transverse; r­m fused with tb and m­cu, slightly oblique. Crossvein m­ cu twice the length of r­m. M 2 probably absent. M 3+4 absent. M 1 straight, weak.

MATERIAL: Holotype PIN 3426 /256, sex unknown. Russia, Taimyr Peninsula , Nizhnyaya Agapa, coll. 1973.

ETYMOLOGY: The species is an epithet in reference to the locality, the Nizhnyaya Agapa River.

COMMENTS: Structure of ocelli and a transverse RS base are apparent characters of generic level, distinguishing the species from T. sibirica , but incomplete preservation of the specimen from Nizhnyaya Agapa does not allow description of a new genus. Both species share such synapomorphies as an incomplete eye bridge, proepimeron apex at the episternal suture, setose metepisternum, and M reduced. Until more specimens of this peculiar group will be found and phylogenetic analysis is done we prefer to keep the species in this genus.

3+4

FAMILY LYGISTORRHINIDAE EDWARDS, 1925

DIAGNOSIS: Eyes round; pedicel bears bristles apically; mouthparts reduced and form proboscis in some genera; Anepimeron fused to katepisternum; Sc very short; R 1 short; stem of M and M fork base absent; r­m aligned with tb; M2 + tb subhorizontal; hind coxae short, hind tibiae and tarsi swollen; metepisternum with deep anterodorsal cleft; gonostyli of simple shape (presumably reversed in Plesiognoriste and Protognoriste ).

Figures

Figs. 4–6. Thereotricha, n.gen. 4. Thereotricha sibirica, n.sp., drawing of amber piece with four embedded specimens, including holotype PIN 3130/183. 5.? T. agapa, n.sp., holotype PIN 3426/256. 6.? T. agapa, head of the holotype.