Drosophilidae, Rondani, 1856

Rampasso, Augusto Santos & O’Grady, Patrick Michael, 2022, Distribution and Taxonomy of Endemic and Introduced Drosophilidae in Hawaii, Zootaxa 5106 (1), pp. 1-80 : 6-8

Key to Major Groups of Drosophilidae in Hawaii

This key has been modified after several previously published keys, including Hardy (1965); Lapoint et al. (2009); Magnacca & O’Grady (2008a); Magnacca & O’Grady (2008b); Markow & O’Grady (2006); O’Grady et al. (2003a); Wheeler (1987). Adventive species are identified to genera. With the exception of the unplaced species in the genus Scaptomyza , all taxa are identified to subgenus.

1. Prescutellar acrostichal setae well-developed; basal scutellar setae divergent; proepisternal setae present, although sometimes small............................................................................................... 2

- Prescutellar acrostichal setae weak or absent; basal scutellar setae usually convergent; proepisternal setae absent.......... 5

2. Arista plumose, with numerous dorsal and ventral rays; C weak or absent beyond end of R4+5.............. Leucophenga

- Arista bare or micropubescent, sometimes with a few short dorsal rays basally; C strong beyond R4+5 to M1............ 3

3. Wings entirely dark or with some darkly clouded areas, giving the flies a “beetle-like” appearance; C between apices of R2+3 and R4+5 with a series of small, thorn-like spines along lower margin; R4+5 and M1 strongly convergent apically... Stegana

- Wing hyaline or with various pigmentation patterns, not clouded as above; no thorn-like spines on C; R4+5 and M1 divergent or parallel, seldom strongly convergent.................................................................... 4

4. Cells bm and dm separated by a crossvein; tan to black flies, with milky white markings on face, postpronotal lobes, and areas below wing bases............................................................................... Phortica

- Cells bm and dm continuous; coloration and markings not as above..................................... Cacoxenus

5. C deeply incised at subcostal break, protruding as a thick black lappet........................................... 6

- Costal lappet absent, C not incised at subcostal break......................................................... 7

6. One pair of dorsocentral setae present; scutellum velvety; body dark above, pale below.................. Mycodrosophila

- Two pairs of dorsocentral setae; anterior dorsocentral inserted far forward, at or near the transverse suture; facial carina very large, antennal bases far apart; acrostichal setulae arranged in two to four rows.......................... Dettopsomyia

7. Head and mesonotum with multicolored vittae....................................................... Zaprionus

- Head and mesonotum either vittate or not, but lacking multicolored vittae........................................ 8

8. Postocellar setae small and inconspicuous; proclinate or inclinate orbital setae arising posterior to, i.e. above, and about equal in size to anterior reclinate orbital setae (Fig. a). Inner margin of forefemur always armed with a row of short teeth................................................................................................... Chymomyza

- Postocellar setae usually well-developed; proclinate orbital setae arising anterior to, i.e. below, anterior reclinate orbital setae and distinctly stronger than it; forefemur rarely armed with a row of teeth......................................... 9

9. Setulae on apex of third antennal segment elongate, about 3x length of basal setulae.................... Hirtodrosophila

- No elongate setulae present on third antennal segment....................................................... 10

10. Male genitalia highly elaborate, sometimes with multiple lobes on epandrium; arista with 0-2 ventral rays, in addition to terminal fork; generally slender flies; habitus unicolorous or with stripes, rarely with elaborate patterns of pigmentation; wings typically hyaline, although sometimes with apical spot or infuscations at crossveins...................... Scaptomyza , 11

- Male genitalia typically lack elaboration; arista with 2 or more ventral rays, in addition to terminal fork, flies tend to be more robust; habitus and wings variable;...................................................................... 27

11. White longitudinal stripe present on scutellum, anteriorly reaching at least to posterior region of mesonotum, often extending along entire length of mesonotum; terminal fork of arista deep, each branch equal in length to dorsal rays of arista............................................................ Scaptomyza (Tantalia) ; see Hardy (1965) for a key to species

- Scutellum and mesonotum may be striped or unicolorous, but never with longitudinal white stripe described above; terminal fork of arista not deep, branches less than length of dorsal rays................................................ 12

12. Rays of arista short; chaetotaxy (e.g., katepisternal and dorsocentral setae) generally reduced; four rows of acrostichal setulae; two well-developed humeral setae................ Scaptomyza (Exalloscaptomyza) ; see Hardy (1966) for a key to species

- Rays of arista elongate; combination of other characters not as above........................................... 13

13. Either zero or one ventral ray present on arista............................................................. 14

- More than one ventral ray present on arista................................................................ 20

14. Eight rows of acrostichal setulae present; female ovipositor sclerotized, may be needle-like and pointed.......................................................... Scaptomyza (Titanochaeta) ; see O’Grady et al. (2003a) for a key to species

- Acrostichal setulae present in two to six rows; female ovipositor fleshy, non-sclerotized, non-dentate.................. 15

15. Arista lacking ventral rays............................................................................. 16

- One ventral ray present on arista........................................................................ 17

16. Head flattened, longer than high; eyes strongly oblique; strong set of presutural dorsocentral setae present................................................................ Scaptomyza (Rosenwaldia) ; see Hardy (1965) for a key to species

- Head nearly square as seen in direct lateral view, lower margin approximately equal in length to the frontal margin; enlarged setulae may be present in presutural position, but not strong... Scaptomyza (Elmomyza) ; see Hardy (1965) for a key to species

17. Two rows of acrostichal setulae present............................................ Scaptomyza (Parascaptomyza)

- Number of acrostichal rows varies from four to six.......................................................... 18

18. Wings with marks over crossveins and at apices of R and M veins................................. Scaptomyza parva

- Wings completely hyaline............................................................................. 19

19. Head broader than thorax......................... Scaptomyza (Alloscaptomyza) ; see Hardy (1965) for a key to species

- Head not broader than thorax............................................................ Scaptomyza taractica

20. Shining black species, thorax and abdomen polished black; two or three ventral rays present on arista; ocellar triangle large, extending to level of proclinate setae; acrostichal setulae present in four rows; clump of black setae on hind trochanter...... Scaptomyza (Bunostoma) ; see Hardy (1965) for a key to species

- Mesonotum brown (black in S. totonigra ), sometimes with longitudinal vittae; acrostichal setulae in six to eight rows; ocellar triangle not enlarged; hind trochanter lacking distinctive black setae............................................ 21

21. Second antennal segment sharply pointed apically, extending over base of third segment; wings distinctly infuscated around veins and margins, central portions of cells mostly hyaline........................................................................................... Scaptomyza (Grimshawomyia) ; see O’Grady et al. (2003a) for a key to species

- Second antennal segment not sharply pointed; wings hyaline or evenly smoky.................................... 22

22. Tibiae yellow with two narrow brown bands, fainter on front tibia..................................................................................... Scaptomyza (Engiscaptomyza) ; see O’Grady et al. (2003a) for a key to species

- Tibiae all yellow, or brown with yellow apices............................................................. 23

23. Palpi greatly enlarged, protruding beyond the oral margin.................................. Scaptomyza magnipalpa

- Palpi not enlarged, enclosed within the oral cavity when mouthparts retracted.................................... 24

24. Epandrium with a prominent anteroventral lobe, over half as high (dorsoventrally) as main portion of epandrium; surstyli long and broad, setulose over the concave medial surface......................................................... 25

- Epandrium lacking a prominent lobe; surstyli not broad and medially setulose; mesonotum brown to black; femora dark brown............................................................................................. 26

25. Thorax entirely yellow; ventral lobe of epandrium broader at apex than at base..................... Scaptomyza vinnula

- Mesonotum and anepisternum rufous, tinged with brown; ventral lobe of epandrium nearly parallel-sided, about as wide at apex as at base........................................................................... Scaptomyza improcera

26. Tibiae all yellow....................................................................... Scaptomyza prolixa

- Tibiae brown except narrow bases and apices............................................... Scaptomyza totonigra

27. Three subequal katepisternal setae present; prescutellar setulae usually present, although can apprear weak in some specimens...................................................................................... Scaptodrosophila

- Middle katepisternal setae either absent or much smaller than anterior and posterior katepisternals.......... Drosophila , 28

28. Yellowish species with a longitudinally striped pleurae; preapical setae absent on second and third tibiae.................................................................................................. D. busckii (Dorsilopha)

- Characters not as above, most notably the pleurae without lateral stripes......................................... 29

29. Small dark species; most setae shortened; antennal segments short; found in tubular flowers (Note: this taxon is similar to Scaptomyza (Exalloscaptomyza) but the genitalia are markedly different)........................ D. alfari (Phloridosa)

- Not as above; body setae and antennal segments not shortened................................................ 30

30. Forelegs of males with regular comb-like structure...................................... melanogaster species group

- Male forelegs not as above, if a comb present, it is highly irregular and more brush-like............................ 31

31. Dark species, each hair arises from a discrete dark spot, although these are fused in some species...... repleta species group

- Species color variable, but without spotted appearance....................................................... 32

32. Three pairs of dorsocentral setae......................................... D. polychaeta ( polychaeta species group)

- Two or fewer pairs of dorsocentral setae present............................................................ 33

33. Anterior scutellar setae divergent; one or both crossveins infuscated; sterno index 0.8-0.9; third costal section of wing with heavy setae on basal half or more.......................................................... virilis species group.

- Not with the above combination of characters.............................................................. 34

34. Abdomen shining, with a distinct dark pattern over tan ground color................... D. cardini ( cardini species group)

- Abdomen may be patterned, but never shiny in appearance unless it is entirely black............................... 35

35. Mostly tan species, although there may be darker pigmentation on abdominal segments; lacking modifications to mouthparts; legs may have peg-like setae but never with elongate setae................................................... 36

- Not as above........................................................................................ 37

36. Larger species; some taxa with peg-like setae on inner margin of femur and/or with a silvery gray frons.................................................................................................. immigrans species group

- Small species, no modifications to forelegs; frons tan, dull......................... D. bizonata ( bizonata species group)

37. Shiny black species; collected around sap fluxes in hot dry areas below 1500ft. ... D. carbonaria ( carbonaria species group)

- Species color variable, from shining black to dull tan to variously pigmented; not associated with hot, dry habitats below 1500ft ............................................................................ 39, Hawaiian Drosophila

38. Shining black species, most with either a lightened tip at the apex of the scutellum or with a sclerotized rim on the labellum or both.......................................... haleakalae species group; see Hardy et al. (2001) for a key to species

- Not shining black, although may have darker patterns of pigmentation on head, thorax and abdomen.................. 39

39. Mouthparts of males heavily modified, with specialized setae, tusks, or other structures; wings may be heavily patterned ( fuscoamoeba group), infuscated at the tips and along crossveins, or entirely hyaline............................................. modified mouthpart species group; see O’Grady et al. 2003b and Magnacca & O’Grady (2009) for keys to species

- Mouthparts not modified, wings variable in infuscation ( D. ornata has modified setae on mouthparts but highly distinctive wing patterns and characteristic setae on male forelegs).......................................................... 40

40. Larger species, wings with elaborate patterns of pigmentation......................................................................................... picture wing species group; see Magnacca & Price (2012) for a key to species

- Mostly small to intermediate sized flies; wings hyaline or only slightly infuscated on the tips of the long veins or crossveins or both, lacking ornate patterns........................................................................... 41

41. Arista inserted preapically.......... ateledrosophila species group; see Magnacca and O’Grady, 2008b for a key to species

- Arista inserted in a normal position...................................................................... 42

42. Front legs of males with various modifications, including spoon-like structures, dense, irregular combs of setae, or elongate cilia; aedeagus lacking preapical hook; female ovipositor short or stout, not elongate; head with normal complement of setae...... AMC Clade; see Hardy (1977), Hardy (1965), Hardy & Kaneshiro (1979), and Lapoint et al. (2009) for keys to species

- Front legs of males may have elongate cilia, but never with spoons or combs of setae; elongate setae, when present, curvate; preapical hook on tip of aedeagus; female ovipositor elongate; head setae greatly reduced in many species.............................................. nudidrosophila species group; see Magnacca and O’Grady, 2008b for a key to species