Pachylophus, Loew, 1858

Deeming, John C., 2018, A revision of the Afrotropical species of Pachylophus Loew (Diptera: Chloropidae) and some related Ovoviviparous genera, Zootaxa 4482 (1), pp. 1-51 : 4-5

Key to Afrotropical and Arabian species of Pachylophus

1 Arista of peculiar structure, the combined lengths of the first and second segments being equal to that of the third. Greater part of pleura, including propleuron, heavily grey dusted. Wing long and narrow............................ aristalis sp. n.

- If the combined lengths of the two basal aristal segments are equal to that of the third ( P. varipes ), then the propleuron, if dusted, is weakly so.................................................................................... 2

2 All sclerites of pleura, including propleuron, uniformly rather weakly dusted, though the part of the katepisternum facing the fore coxa is shining and in worn specimens the vertically ridged area of anepisternum adjacent to anterior spiracle may be also.................................................................................................... 3

- Except for the shining propleuron and at least anterior one third to one half of anepisternum, other sclerites wholly or partially dusted, often intensively so.............................................................................. 4

3 Predominantly black species with femora black on greater part of their length........................ splendidus Adams

- Predominantly brownish yellow species with legs dusky yellow and only obscure darkening of femora....... frontalis Loew

4 Frontal triangle partially dusted, even if only between the ocelli................................................. 5

- Frontal triangle completely undusted..................................................................... 11

5 Frons distinctly produced in front of eye and occiput with a distinct flange-like dilation, so that head is considerably longer than deep. Frontal triangle with its sides much longer than its base and with dusting only between ocelli. Anepisternum with a small patch of dust on its posterodorsal corner. Gena extensively undusted........................................ 6

- Frontal triangle either much shorter or more extensively dusted or both........................................... 7

6 Frontal triangle black, at mid-length often with an encroachment of pilosity onto the extreme lateral margins. Face black on antennal grooves and along ptilinal suture.................................................. femoratus (Johnson)

- Frontal triangle yellow, black only on ocellar prominence. Face yellow throughout...................... flavipes (Lamb)

7 Frontal triangle predominantly shining. Anepisternum undusted................................................. 8

- Frontal triangle predominantly dusted. Anepisternum either extensively dusted on its posterior half or bare.............. 9

8 Frontal triangle dusted only between the ocelli, short, not extending to apical one fifth of frons. Postpedicel hardly longer than deep, rounded with slightly obtuse dorsoapical angle.............................................. minimus Becker

- Frontal triangle dusted on ocellar prominence and on a field as large as ocellar prominence on either side of it, its anterior extremity broadly rounded. Postpedicel about 1.5 times longer than deep, with rather acute dorsoapical angle................................................................................................... gallagheri Deeming

9 Anterior extremity of the completely black frontal triangle rounded, the dusting consisting of two broad, somewhat concave swathes, sometimes connected but usually separated by a fine median ridge and extending almost to margins. Mouth margin with a distinctive shining black triangle which has its point on the lower eye margin. Slender species with ground colour of pleura black throughout..................................................................... inornatus Loew

- Anterior extremity of the frontal triangle acute. Parafacial and gena entirely dusted. Robust species with pleura not entirely black.............................................................................................. 10

10 Frontal triangle usually with its margins and the ocellar prominence black, the remainder of its surface paler in ground colour and dusted, if uniformly dark then lacking both a medial furrow and a medial shining area. In rare instances the dusting reduced to a small field on either side of ocellar prominence...................................... punctifrons Becker

- Frontal triangle dark throughout, typically dusted on all but a long shining black medial diamond-shaped marking extending from anterior ocellus to apex and covering a deep longitudinal furrow, in isolated examples the furrow may be absent and the dusting surrounding it more restricted in extent.................................................. pollinosus sp. n.

11 Scutellum of peculiar structure, in dorsal view trapezoid, apically with a small median stud-like projection and a smaller one on either apicolateral corner, these latter bearing a weak seta. Surface of scutellum rugose........................... 12

- If scutellum with a truncated apex it is lacking such projections and has apicolateral angles slightly rounded, its surface sometimes shagreened, only rarely rugose..................................................................... 13

12 Femora brownish black. Scutum with a very distinctive and strongly differentiated pattern of grey dust on a black ground colour and with a line of dust along suture connecting the dorsocentral line to the intraalar line).......... proximus Adams

- Legs unicolorous dirty yellow to brownish yellow. No such connecting sutural band present......... punctifemur Sabrosky

13 Posterodorsal half of anepisternum bearing numerous short dark setulae (but in material that has been preserved in spirit these may have become pale and very difficult to see). Dusting of the parafacial and gena restricted to a swath above the vibrissa, which becomes a narrow band under the eye. Yellowish species................................... pellucidus Becker

- Such setulae lacking. Gena either with mouth rim undusted or with a small shining triangle, but never as extensively shining as this................................................................................................ 14

14 Entire anepisternum, anepimeron and katepisternum shining, this last with total height of posterior two thirds of its length covered in long pale setulae. A predominantly black species with legs inclusive of coxae yellow, but all femora black on all but their extreme bases and apices................................................................ beckeri Curran

- If there are pale setae on the katepisternum, then these are confined to ventrally-facing parts and that sclerite is not entirely devoid of dusting..................................................................................... 15

15 Upper edge of anepisternum below the single notopleural seta with a small depressed area bearing 4 to 5 groups of compact black setulae, under light microscopy appearing as vertical ridges which are separated from each other by approximately their own width. Yellow species with unprojecting frons, the frontal triangle equilateral, and having a dark lyre-shaped marking extending from neck to bases of inner vertical setae................................................. ismayi sp. n.

- Although the anterior part of the anepisternum may bear some folds or ridges, such a specialised development is absent from the upper margin..................................................................................... 16

16 Anepimeron entirely heavily grey dusted.................................................................. 17

- Anepimeron at least partially shining..................................................................... 19

17 Propleuron and anepisternum black and totally undusted except for a small field of dusting on the upper posterior corner of the latter, in strong contrast to the completely heavily grey dusted surrounding sclerites. Frontal triangle black, longer than broad, flat and straight-sided................................................................................. 18

- Katepisternum also undusted on its upper part to level of upper extremity of the mid coxa. Frontal triangle black, in form of an equilateral triangle and with a preapical depression.............................................. nigeriensis sp. n.

18 Frons fully twice as long as its width at mid length. Legs entirely yellow. Wing greyish hyaline............. varipes Adams

- Frons at mid length one and a half times as long as wide. All femora infuscate except at extreme apex. Wing more fumose, though not as intensively so as in P. lugens ................................................... tschirnhausi sp. n.

19 Femora deep black, the tibiae and tarsi predominantly brown to black. Haltere and frontal triangle black, this latter with a deep median groove. Wing heavily blackish tinged. Combined parafacial and gena narrow, not deeper than the breadth of the arista........................................................................................... lugens Loew

- Legs yellow, frequently with fore tibia and tarsus and apical tarsomeres of other legs somewhat infuscate. If femora are also somewhat infuscate they are not deep black................................................................ 20

20 Thorax entirely deep black in ground colour. Haltere partially or completely black................................. 21

- Thorax dirty yellow to brown in ground colour, or with both colours represented, with or without black markings........ 22

21 Katepisternum dusted only on part anterior to and on a level with mid coxa. Frontal triangle with a distinct preapical depression................................................................................... fossulatus Adams

- Katepisternum dusted throughout its whole height. If frontal triangle with a preapical depression it is usually not as profound........................................................................................ halteratus Becker

22 Postpedicel apically produced, similar in structure to that of Pseudogaurax and Gampsocera . Frontal triangle with an anterior and a posterior depression, the two separated by a transverse ridge. Dusting of pleura weak and confined to meron. Anterior leg yellow with tibia and basitarsomere black and apical four tarsomeres creamy white...................... mirabilis sp. n.

- None of these characters apply.......................................................................... 23

23 Wing conspicuously grey fumose with costal cell cream coloured in strong contrast to it................ lacteibasis sp. n.

- If the base of the costa is obscurely yellow, the costal cell is not in strong colour contrast to the rest of the wing.......... 24

24 Postpedicel rather short. Frontal triangle short, black and with a deep depression between anterior ocellus and apex. Face entirely yellow. Postpronotal lobe undusted with a shining black spot............................... stuckenbergi sp. n.

- Postpedicel kidney-shaped, longer than deep. Never with combination of black frontal triangle and yellow face.......... 25

25 Scutellum black on either side of a dirty yellow median line. Frontal triangle with margins suffused with brown and ocellar prominence black. Only a low extension of the mouth margin shining. Postpronotal lobe and scutum dusted, this latter with a distinct darkening of ground colour on a broad median band from neck to suture, thereafter decreasing in intensity............................................................................................... contractus Becker

- Scutellum lacking a contrasting pale medial line. Frontal triangle uniformly yellow, black only between the ocelli. Silvery-grey dusting of combined parafacial and gena restricted to a triangle extending from vibrissa to middle of lower eye margin. Postpronotal lobe and large part of the entirely pale scutum shiny...................................... obscurior Becker