Subgenus Titanochaeta Knab, 1914

24. Arista with one ventral ray; male surstylus without a posterior spine; female ovipositor sometimes blunt....................................................................................................................................................................25

- Arista without ventral rays, or if one present (rarely in S. chauliodon), the male surstylus bears a prominent black posterior spine; female ovipositor always pointed, needle-like..............................................26

25. Pleura and sometimes femora dark brown to black; surstyli fused to epandrium (female unknown). Hawai‘i, Maui ......................................................................................... S. (Titanochaeta) canuta (Hardy)

- Pleura and femora entirely yellow; surstyli not fused to epandrium; female ovipositor blunt. O‘ahu.......... ............................................................................................................ S. (Titanochaeta) contestata (Hardy)

26. Crossveins distinctly infuscated; M between crossveins dm–cu and r–m short, about 1/5 length of M measured from crossvein dm-cu to apex. Maui, O‘ahu, Kaua‘i .................... S. (Titanochaeta) swezeyi (Wirth)

- Crossveins not infuscated; M between crossveins dm–cu and r–m greater than 1/5 the length of M between dm–cu and apex...........................................................................................................................27

27. Sides of scutellum with conspicuous setae in addition to anterior and posterior scutellars; both katepisternal setae well developed, roughly subequal in length ............................................................................. 28

- Scutellum lacking secondary setae; length of anterior katepisternal setae variable, ranging from short to subequal setae............................................................................................................................................29

28. Mesonotum and scutellum entirely yellow, abdomen predominantly yellow. Southern O‘ahu, Hawai‘i, Maui, Moloka‘i, Lāna‘i ............................................................................ S. (Titanochaeta) bryani (Wirth)

- Mesonotum mostly black in ground color, covered with gray pollen; scutellum black, abdomen mostly black. Moloka‘i, Hawai‘i ............................................................ S. (Titanochaeta) setosiscutellum (Hardy)

29. Anterior katepisternal strong, about equal in length to posterior katepisternal setae; surstyli bear a strong black spine at the apex of a prominent posterior projection; apical fork of arista long or bifid, giving the appearance of a ventral ray. Maui, O‘ahu ........................................ S. (Titanochaeta) chauliodon (Hardy)

- Anterior katepisternal not over 1/2 length of posterior, usually small and hair-like; male genitalia not as above; arista with short terminal fork, never long or bifid.......................................................................30

30. Mesonotum predominantly yellow with three narrow brown vittae extending the full length; incomplete

brown vittae present on the pleurae; scutellum with a brown spot extending over basal 1/2; abdomen dark brown, distinctly marked with yellow. Kaua‘i ...................................... S. (Titanochaeta) vittigera (Hardy) - Predominantly black species, mesonotum and scutellum entirely black in ground color, lacking vittae. 31

31. First two abdominal segments almost entirely yellow..............................................................................32

– Abdomen almost entirely black, a narrow yellow band may be present at apex of second tergum..........34

32. Tergites 3 and 4 shining black, 5 and 6 yellow; epandrium about 2 times longer than high, truncated ventrally; no projection along medial surface of surstylus visible in ventral view. Moloka‘i ........................... ................................................................................................... S. (Titanochaeta) neoevexa O’Grady et al.

- Abdomen predominantly brown or black; epandrium about 2 times higher than long, tapered ventrally; moderate to strong projection on medial surface of surstyli in ventral view............................................33

33. Abdominal tergites 4 to 6 brownish yellow on lateral margins, darker on dorsum; male genitalia brownish yellow; pleura largely brown; surstyli, when observed in lateral view, with sharply pointed projection on mediolateral surface and sharply pointed spine-like process on posterior margin. Hawai‘i ........................ ............................................................................................................ S. (Titanochaeta) ichneumon (Knab)

- Abdominal tergites 4 to 6, including genitalia, predominantly shining black; pleura entirely yellow; surstyli, when observed in lateral view, lacking sharply pointed projection on mediolateral surface, process on posterodorsal surface of surstyli broad, not spine-like and pointed. Kaua‘i ................................................. ........................................................................................... S. (Titanochaeta) neokauaiensis O’Grady et al.

34. Abdomen shining black beyond second tergite; male genitalia yellow; anterior reclinate inserted near lower 1/3 of fronto-orbital plate. Maui ................................................... S. (Titanochaeta) glauca (Hardy)

- Abdomen black, dusted with gray; male genitalia black; anterior reclinate inserted near middle of fronto orbital plate. Hawai‘i ........................................................... S. (Titanochaeta) neosilvicola O’Grady et al.