Electroxylomyia eocenica, Nel & Prokop, 2006

Nel, André & Prokop, Jakub, 2006, New fossil gall midges from the earliest Eocene French amber (Insecta, Diptera, Cecidomyiidae), Geodiversitas 28 (1), pp. 37-54 : 49-52

Electroxylomyia eocenica n. sp. ( Fig. 5 )

TYPE MATERIAL. — Holotype specimen PA 3004 1/8 (male), allotype specimen PA 3004 2/8 (female), in the same piece of amber with two Hymenoptera , three insect larvae and an arachnid. Paratype specimen PA 5468 1/2 (female), together with a Diptera Psychodidae .

ETYMOLOGY. — After the Eocene age of the fossils.

DIAGNOSIS. — That of the genus.

DESCRIPTION

Head 0.16 mm long, 0.15 mm high; eyes well separated, rounded, 0.12 mm diameter; ocelli absent; antenna 0.37 mm long, scape 0.3 mm long, 0.2 mm wide, pedicel 0.3 mm long, 0.2 mm wide, 11 flagellomeres in both male and female, of nearly the same size, all longer than wide (0.3 mm long, 0.1 mm wide in male; 0.2 mm long, 0.1 mm wide in female), and with a distinct neck in male (ratio length of node/length of neck = 2), neck inconspicuous in female, last flagellomere 0.15 mm long, flagellomeres not band-shaped or digitate, horseshoe-shaped, without visible star-like or fanlike sensorium, palpus very strongly reduced, not visible in both male and female, absent or with only one segment.

Thorax 0.25 mm long, 0.20 mm high, longer than broad.

Wing 0.76 mm long, 0.25 mm wide (male), 0.95 mm long, 0.35 mm wide (female), hyaline, macropterous, wing membrane with few visible macrotrichia, wing margin with numerous long macrotrichia; Costa continuing around wing; humeral vein absent; subcostal vein very close to R, incomplete, 0.30 mm long (female), not reaching wing margin; vein R1 0.43 mm long (female); R5 simple, not thickened, vanishing in wing membrane 0.17 mm from posterior wing margin (female); Rs emerging from R 0.10 mm from wing base; Rs basal of cross-vein r-m very short (0.01 mm long); part of vein M distal of fusion with Rs absent; CuA simple, vanishing in wing membrane 0.03 mm from posterior wing margin; CuP absent; A1 and A2 absent.

Haltere with large knob, 0.04 mm wide and 0.08 mm long, and stem 0.10 mm long, bare.

Legs slender, without visible scales but with numerous short setae; fore femur 0.20 mm long, tibia 0.22 mm long, tarsi 0.21 mm long; mid femur 0.18 mm long, tibia 0.19 mm long, tarsi 0.19 mm long; hind femur 0.24 mm long, tibia 0.27 mm long, tarsi 0.20 mm long; femora and tibiae not swollen; tibial spurs absent; all legs with five tarsomes, tarsomere 1 much shorter than 2, fifth tarsal segment only slightly longer as fourth, without sensorial bristles on the ventral surface.

Abdomen (male) 0.50 mm long, 0.10 mm wide, mid part; genital appendages poorly visible, but gonostyles with few small hairs and no claw at apex.

Abdomen (female) elongate, 0.80 mm long, 0.15 mm wide in mid part, cercus two-segmented, 0.45 mm long.

DISCUSSION

After Wood & Borkent (1986, 1989), Electroxylomyia eocenica n. gen., n. sp. falls in the Cecidomyiidae rather than in Sciaridae , because of the following synapomorphies: presence of an eye bridge (character also present in Sciaridae and Scatopsoidea), tibial spurs absent (see also Gagné 1994) (but character also present in Scatopsidae ); setae of flagellomeres arranged in encircling whorls. After the partial phylogenetic analysis of the cecidomyiid subfamilies of Jaschhof (2000), Electroxylomyia n. gen. has the two synapomorphies of the Porricondylinae + Cecidomyiinae , viz. the lack of ocelli and first tarsomeres shortened. Following the key to dipteran families of McAlpine (1981), Electroxylomyia n. gen. falls in the Porricondylinae because of the following characters: vein A2 absent, R with only two branches, C continuing around wing, ocelli absent, tarsomere 1 much shorter than 2, M1+2 absent, R5 as strong as other veins, female cercus two-segmented. Following the keys to Nearctic and European genera proposed by Gagné (1981, 1994) and Skuhravá (1997), Electroxylomyia n. gen. shares with the Heteropezini its wing veins greatly reduced and CuA simple. But similarly reduced wing can be found in some Winnertziini ( Mamaev & Zaitzev 1998) . Also, both the male and female of Electroxylomyia n. gen. have eleven flagellomeres, instead of 10 or less as in recent Heteropezini . This last character would exclude affinities with this last tribe.

Within the Porricondylinae with more than 10 flagellomeres, Electroxylomyia n. gen. would fall in the Winnertziini because it has only 11 flagellomeres, and no circumfila on its flagellomeres. Thus, we tentatively attribute it to this tribe rather than to the Heteropezini . Nevertheless, a phylogenetic analysis of the whole subfamily Porricondylinae is necessary before any definite conclusion. Electroxylomyia n. gen. could as well have been a Heteropezini with 11 flagellomeres.

After the key to genera of Winnertziini of Mamaev & Zaitzev (1998), Electroxylomyia n. gen. could fall in Kronomyia Felt, 1911 because of the following characters: fifth tarsal segment only slightly longer as fourth, without sensorial bristles on the ventral surface; no band-shaped or digitate, horseshoe-shaped sensorium on flagellomeres; antennae of male with 2 + 11 segments, as in female. But Electroxylomyia n. gen. strongly differs from Kronomyia in its vein M absent and its palpus very strongly reduced, not visible, absent or with only one segment ( Parnell 1971; Skuhravá 1997). Electroxylomyia n. gen. differs from Rhipidoxylomyia Mamaev, 1964 in its median veins absents and in the absence of star-like or fan-like sensorium on flagellomeres ( Mamaev 1964). It differs from Clinorrhytis Kieffer, 1896 in its male antennae 11-segmented and its vein M absent ( Kieffer 1913). It also differs from Sylvenomyia Mamaev & Zaitzev, 1998 in its male antennae 11-segmented. It differs from Winnertzia Rondani, 1861 and Parwinnertzia Felt, 1919 in the absence of digitate, horseshoe-shaped sensorium on flagellomeres. Electroxylomyia n. gen. shares with Cryptoxylomyia Mamaev & Zaitzev, 1998 the reduction of the mouth parts and that of wing venation, but it has no trace of forked or digitate sensorium on flagellomeres, unlike this last genus.

Electroxylomyia n. gen. differs from the fossil genus and species Cretowinnertzia angustala Gagné, 1977 (Late Cretaceous amber of Canada) in its female antenna with 11 flagellomeres instead of ten, and its palpus strongly reduced instead of being foursegmented ( Gagné 1977).

Evenhuis (1994) listed four species of Winnertzia in the late Eocene Baltic amber, viz. W. affinis Meunier, 1904 , W. cylindrica Meunier, 1904 , W. radiata Meunier, 1904 , and W.separata Meunier, 1904 . These species are rather poorly described and their exact generic position remains uncertain because several characters diagnostic of the genus Winnertzia are not recorded in Meunier (1904). W. radiata differs from Electroxylomyia n. gen. in the presence of 12 flagellomeres in female and four-segmented and rather long palpus ( Meunier 1904: 25, 26, pl. 4, figs 7, 8). W. cylindrica differs from Electroxylomyia n. gen. in the same characters, plus the presence of a free vein M ( Meunier 1904: 26, pl. 4, figs 9, 10). Meunier (1904: 27) indicated that W. affinis is very similar to W. cylindrica , the differences between the two concerning the relative lengths of the tarsomeres. W. separata differs from Electroxylomyia n. gen. in the presence of four-segmented palpus ( Meunier 1904: 27). Winnertzia burmitica (Cockerell, 1917) , from the upper Albian Burmese amber, is the oldest record of the tribe. It has large, three-segmented palpus and antennae probably 12- jointed, unlike Electroxylomyia n. gen. Fedotova & Perkovski (2005) described Winnertzia bellata and W. isotoma from the Rovno amber. They differ from Electroxylomyia n. gen. in their broader wings with more complete venation.

Figures

FIG. 5. — Electroxylomyia eocenica n. gen., n. sp., holotype (PA 3004 1/8), general habitus: A, drawing; B, photograph. Scale bars: A, 0.3 mm; B, 0.25 mm.