Isoneuromyia Brunetti

Evenhuis, Neal L., 2006, New species of Isoneuromyia Brunetti (Diptera: Keroplatidae) from the Oriental Region, Zootaxa 1140, pp. 1-29 : 2-8

Isoneuromyia Brunetti

Isoneuromyia Brunetti, 1912: 66 . Type species: Isoneuromyia annandalei Brunetti, 1912 , by subsequent designation ( Edwards, 1925: 166).

Isoneuromyia is a keroplatid genus of over 50 species found primarily in the Oriental and Neotropical Regions, with a few species also found in the Palaearctic, Nearctic, and Australasian/Oceanian Regions. They vary in size but can range from some of the largest keroplatids known (over 18 mm in length) to smaller species less than 5 mm in length. All have strong brown wing veins and elongate abdomens. Some are wasp mimics, where species have the terminal abdominal segments expanded and flattened (cf. Figs. 27–28 ). Nothing is known of their larval habitats.

Brunetti (1912: 66) described Isoneuromyia based on two included species: I. annandalei and I. rufescens but did not designate a type species. Most authors subsequently treated the type fixation as I. annandalei by monotypy, having missed the fact that I. rufescens was described in the same work, but in the Appendix on p. 559. E dwards (1925: 166) was the first to make a formal subsequent designation of I. annandalei as the type species.

Brunetti (1912) distinguished Isoneuromyia from Platyura and other Indian keroplatids by the strong wing venation. However, this character is also found in species in other genera of Keroplatidae , and thus by itself cannot be used to distinguish the genus. The following characters used to distinguish Isoneuromyia in keys by Hutson et al. (1980), Chandler & Ribeiro (1995), Soli et al. (2000), and Vockeroth (in press) include laterotergite, mediotergite, and anepimeron bare; tibiae with spines in regular rows throughout; costal vein not extending past R5; vein A1 almost reaching wing margin; and bases of forked veins with minute spines (sometimes only seen under high magnification). Matile (1990) treated the shape of the male genitalia as a “primitive” condition, consisting of macrocerine­looking gonostyli with normally bidentate apices (cf. Figs. 34 –43).

Additional characters that may be useful in distinguishing Isoneuromyia from other genera and in distinguishing species within the genus have been found in the species from the Oriental Region in this study and are briefly annotated below.

Head

Facial shape: The face is produced to varying degrees and slightly hook shaped in lateral view ( Figs. 1–2 ), which is reminiscent of Platyura facial characteristics. Species of Truplaya Edwards also have this character state but can be distinguished from Isoneuromyia by the tibial spines being irregularly arranged basally (in regular rows along entire length of tibia in Isoneuromyia ).

Palpi: The palpi have similar shapes all through the genus but coloration can differ among species (from all brown to all yellow).

Antennae: The antennal segmental shapes are fairly consistent throughout the species examined. The only variation found is in coloration. In the Oriental species, the color of the apical flagellomeres can be of significance. Some species have the flagellomeres unicolorous, while others have bicolored antennae (i.e., the basal flagellomeres are a contrasting color to the apical flagellomeres) (cf. Figs. 3–6 ).

Thorax

Prescutellar shape: Two types have been found in the specimens examined from the Oriental Region: 1) a normal type tapering from the postalar calli to the scutellum and with the scutellum relatively normal in shape and size ( Fig. 11 ); and 2) a flared condition in which the prescutellum has developed into a shield­like structure slightly covering a very minute scutellum ( Fig. 13 ).

Mesonotal pattern: Most species examined in this study from the Oriental Region have a pattern of two admedian stripes and a central median stripe. These may be coalesced into one ( Fig. 13 ); all separate ( Fig. 15 ); or with the median stripe faded, reduced, or absent altogether ( Fig. 12 ). Other species have a unicolorous mesonotum (cf. Fig. 18 ). These differences may not be of phylogenetic significance but can be useful in distinguishing species.

Legs

Tibial spurs: Tibial spur color is predominantly brown to black; however, there is a group of species from Borneo and Sulawesi that have orange to yellow tibial spurs. Further study is needed to determine if this character state is of phylogenetic significance.

Wing

Venation: All veins are strong and brown to dark brown in color. Brunetti (1912) did not indicate if the veins all reached the wing margin, but his illustrations of grandis and annandalei seem to indicate that at least veins M2 and A1 do not reach the wing margin. In all of the specimens examined in this study, vein M2 did not reach the wing margin. Most had veins M2 and CuA1 not reaching the wing margin. Some additionally had CuA2 and A1 not reaching the margin. Vein M1 almost always reaches the margin but has the sclerotization much weakened at the apex of the vein.

Infuscation: Essentially two types of wing infuscation occur in the specimens examined: 1) a distinct area of infuscation subapically that may extend to the wing margin as a paler color or the same color (cf. Figs 20–22, 24, 26 ); and 2) no infuscation except at most yellowish to pale brownish tinting along the anterior costal margin as far as the tip of the wing (cf. Figs. 23, 25 ).

Abdomen

Shape of terminal segments: In some species, the terminal abdominal segments are flattened laterally and expanded, which may be a form of mimicry with a wasp. Models have not been found in this study; however, Edwards (1933) described I. polybioides as a mimic of the wasp Polybioides raphigastra (de Saussure), the specimen of which was placed in the same collection alongside the keroplatid by its collector because of the presumed mimicry.

Male genitalia

Gonostylus: Slight differences have been found among most of the species examined in this study, the most notable being coloration, levels of pilosity, and two Laotian species ( brunettii , n. sp.; glabra , n. sp.) having the gonostylus multidentate (Figs. 35–36) instead of the typical bidentate condition. Two species ( nigerrima , n. sp.; variabilis , n. sp.) have a short peg­like tooth in close association with but separate from the lower of the two teeth in the otherwise bidentate condition.

Female genitalia

Cerci: Of the few female specimens examined in this study, some species have the cerci small and subhemispherical in shape ( Fig. 10 ), while others have the cerci considerably elongated ( Fig. 9 ), the latter of which may be an adaptation to specialized oviposition habits.

Figures

FIGURE 34. Isoneuromyia splendida, n. sp. A. Male genitalia, dorsal view. B. Detail of apex of gonostylus, showing minute teeth in between larger teeth.

FIGURES 27 – 33. 27 – 30. Isoneuromyia habituses, lateral view showing thoracic and abdominal shapes and patterning, legs beyond coxae removed and wing venation not shown. 27. I. brunettii, n. sp. 28. I. variabilis, n. sp. 29. I. nigerrima, n. sp. 30. I. pallidopsis, n. sp. 31 – 33. Isoneuromyia abdomens, dorsal view showing patterning. 31. I. splendida, n. sp. 32. I. subapicalis, n. sp. 33. I. nigribasis, n. sp.

FIGURES 1 – 6. 1 – 2. Isoneuromyia heads, lateral view, showing general shapes, antennal flagellomeres and vestiture removed. 1. I. splendida, n. sp. 2. I. yorki, n. sp. 3 – 6. Isoneuromyia antennae, lateral view. 3. I. nigerrima, n. sp. 4. I. splendida, n. sp. 5. I. polybioides (Edwards). 6. I. glabra, n. sp.

FIGURES 11 – 19. Isoneuromyia thoraces, dorsal view. 11. I. brunettii, n. sp. 12. I. flava, n. sp. 13. I. glabra, n. sp. 14. I. matilei, n. sp. 15. I. nigribasis, n. sp. 16. I. pallidopsis, n. sp. 17. I. splendida, n. sp. 18. I. xanthina (Edwards). 19. I. yorki, n. sp.

FIGURES 20 – 26. Isoneuromyia wings, showing apical patterning. 20. I. splendida, n. sp. 21. I. subapicalis, n. sp. 22. I. nigribasis, n. sp. 23. I. glabra, n. sp. 24. I. nigerrima, n. sp. 25. I. jata, n. sp. 26. I. yorki, n. sp.

FIGURES 7 – 10. 7. Isoneuromyia splendida, n. sp., thorax, lateral view, vestiture removed. 8. Isoneuromyia variabilis, n. sp., apex of fore tibia showing tibial pecten in association with tibial spur. 9 – 10. Isoneuromyia female terminal abdominal segments, showing relative lengths of cerci. 9. I brunettii, n. sp. 10. I. yorki, n. sp.