Endochironomus eocenicus, Published, 2007

Published, First, 2007, Chironomid midges from early Eocene amber of France (Diptera: Chironomidae), Zootaxa 1404, pp. 1-66 : 44-46

Endochironomus eocenicus n. sp.

( Figs. 41, 42)

Etymology: This species is named after the Eocene period.

Diagnosis: Dorsomedial extension of eyes strong, extending to inner margin of pedicel; male antenna with 13 flagellomeres; antennal ratio important (> 0.35); RM oblique to R 4+5; squama with setae; scutum extending to apex of antepronotal lobes; fore tibial scale well developed and bearing spine but not spur; fore tarsus with rather long beard; mid and hind tibiae with 2 spurs, 1 on each comb; median volsella absent; tergite VIII not anteriorly tapered.

FIGURE 42. Endochironomus eocenicus n. sp., holotype PA 2267, drawing of habitus (scale bar = 1 mm), drawing of male genitalia (scale bar = 0.1 mm).

Description: Head 0.40 mm long; ocelli absent; antenna 0.82 mm long, much longer than head, distinctly hairy, with 13 flagellomeres covered with long setae (shortest 0.04 mm long, longest 0.4 mm long), antennal ratio 1.54 (> 0.35), pedicel broad and short, rounded, 13 th flagellomere 0.5 mm long; eye bare but deformed, with strong dorsomedial extension, extending to inner margin of pedicel; mouthparts lacking functional mandibles; all palpomeres with numerous setae; 1 postocular seta, frontal and inner vertical and outer vertical setae not visible. Thorax 0.68 mm long, 0.54 mm high; postnotum without setae but with distinct longitudinal median groove; surface of scutellum with numerous long setae; scutal tubercle not visible; 2 prealar setae; 1 supraalar seta; anterior acrostichal setae not visible; series of numerous dorsocentral setae; postanepisternal setae absent; preepisternum bare. Wing macropterous, apically rounded, 1.12 mm long, 0.34 mm wide, hyaline, without macrotrichia; anal vein An 2 absent; radius with 3 branches R 1, R 2+3 and R 4+5, R 2+3 weakly sclerotized apically and not divided into R 2 and R 3; costa ending at level of insertion of last branch of radius; only M 1+2 and M 3+4 present; cross­vein MCu absent; squama with 5 visible setae. Halter 0.16 mm long. Fore femur 0.58 mm long, tibia 0.34 mm long, tarsus 1.64 mm long; mid femur 0.6 mm long, tibia 0.52 mm long, tarsus 0.74 mm long; hind femur 0.58 mm long, tibia 0.52 mm long, tarsus 0.98 mm long; fore tibial scale well developed, bearing spine, not spur; mid tibia with 1 spur, hind tibia with 2 spurs, 1 on each comb, combs closely approximated but separated; ta4 of all legs cylindrical, not cordiform; fore tarsus with rather long beard, ratio (length of longest setae/width of tarsomere) 2.5; claw of middle legs simple, as in fore and hind legs. Abdomen 1.44 mm long, 0.18 mm wide; gonostylus with long setae, 0.12 mm long, 0.02 mm wide; fused to gonocoxite 0.05 mm long, 0.01 mm wide, with long setae; anal point sharp and long, 0.05 mm long; inferior volsella narrow and elongate, 0.07 mm long; median volsella absent.

Discussion: In the key to dipteran families of McAlpine (1981), this fossil falls in the family Chironomidae . In the keys to Nearctic genera of Oliver (1981), the key to Holarctic subfamilies of Oliver & Dillon (1989), and the key to Palaearctic subfamilies in Saether et al. (2000), it falls in the subfamily Chironominae because of the following characters: macropterous, wings extending posterior to first abdominal segment; cross­vein MCu absent; tarsomere ta5 not trifid; gonostylus rigid, fused to gonocoxite; fore tarsomere ta1 longer than fore tibia; and hind tibial comb consisting of fused spines. In the key of Cranston et al. (1989), the species is in the tribes Chironomini & Pseudochironomini Saether, 1977 , because the wings are devoid of macrotrichia and RM is oblique to R 4+5. In the key for subfamilies and tribes of Chironomidae of Saether (1977a), our fossils fall in the Chironomini because of the following characters: apex of fore tibia with a scale, with a spine, and without a comb­like spur; and in the genus Endochironomus Kieffer, 1918 , for its apically rounded wings, male antenna with 13 flagellomeres, fore tibial scale well developed and bearing a spine but not a spur, antennal ratio of 1.54, antepronotum not extending anterior more than most anterior projection of scutum, median volsella absent, squama with five visible setae but possibly bearing more, tergite VIII not anteriorly tapered, scutum extending to apex of antepronotal lobes, dorsomedial extension of eyes strong, extending to inner margin of pedicel, mid and hind tibiae with two spurs, one on each comb, and fore tarsus with rather long beard. Grodhaus (1987) revised the Nearctic members of Endochironomus and relatives. He characterized Endochironomus based on the presence of two spurs on the mid tibia and the male fore tarsus with a beard.

The systematics of this genus are still confusing. A comprehensive revision is needed for the non­Nearctic fauna ( Spies & Saether 2004). Thus, it is not possible to compare our fossil with the recent species of Endochironomus , but because it is the first pre­Holocene record of this genus, we recognize a new species for it.

Material: Holotype PA 2267 2/2, paratype PA 7546, both males.