Scaptomyza (Titanochaeta)

O’Grady, Patrick, Bonacum, James, Desalle, R. & Val, Francisca Do, 2003, The placement of Engiscaptomyza, Grimshawomyia, and Titanochaeta, three clades of endemic Hawaiian Drosophilidae (Diptera), Zootaxa 159 (1), pp. 1-16 : 12-14

Scaptomyza (Titanochaeta)

Diagnosis. Titanochaeta was erected by Knab (1914) as a genus of endemic Hawaiian Drosophilidae . Hardy (1965) suggested that this genus actually should be considered a subgenus of Scaptomyza based on a variety of morphological characters including conspicuous surstyli which project well beyond the margins of the ninth tergite ( Fig. 3 ), lack of ventral rays on the arista, and a short head which is approximately two times higher than long. We are placing the eleven known species of Titanochaeta , all of which are parasitic on spider egg sacs, in a subgenus of Scaptomyza . Chaetotaxy is an important synapomorphy of the subgenus Titanochaeta . These species have eight rows of acrostichal setulae, a character not seen in the other species of Scaptomyza . Furthermore, the setae on the head and thorax are very strong, the vertical setae are often longer than the head is wide. The shape of the head is also characteristic. It is equal to or narrower than the thorax in width, with a distinctly oblique, slanted front which is often more than two times longer than the lower margin of the head. The genae are straight sided and indented along the anterior eye margin. Finally, the ovipositor of most taxa is long and needle­like, probably due to the parasitic lifestyle of these taxa.

Discussion. The new subgeneric status of Titanochaeta in Scaptomyza requires that we propose new replacement names for T. evexa , T. kauaiensis , and T. silvicola because those specific epithets are preoccupied in the genus Scaptomyza . We propose: Scaptomyza neoevexa O’Grady et al. , new replacement name for Titanochaeta evexa ( Hardy, 1965) (preoccupied by Scaptomyza evexa Hardy, 1965 ), Scaptomyza neokauaiensis O’Grady et al. , new replacement name, for Titanochaeta kauaiensis ( Hardy, 1965) (preoccupied by Scaptomyza kauaiensis Hackman, 1959 ), and Scaptomyza neosilvicola O’Grady et al. , new replacement name, for Titanochaeta silvicola ( Hardy, 1965) (preoccupied by Scaptomyza silvicola Hardy, 1965 ).

Included Taxa. Scaptomyza (Titanochaeta) bryani (Wirth) , comb. nov. from Hawai‘i, O‘ahu, and Maui Nui, S. (Titanochaeta) chauliodon (Hardy) , comb. nov. from Maui and O‘ahu, S. (Titanochaeta) contestata (Hardy) , comb. nov. from O‘ahu, S. (Titanochaeta) glauca (Hardy) , comb. nov. from Maui, S. (Titanochaeta) ichneumon (Knab) , comb. nov. from Hawai‘i, S. (Titanochaeta) neoevexa O’Grady et al. , from Moloka‘i, S. (Titanochaeta) neokauaiensis O’Grady et al. , from Kaua‘i, S. (Titanochaeta) setosiscutellum (Hardy) , comb. nov. from Hawai‘i and Moloka‘i, S. (Titanochaeta) neosilvicola O’Grady et al. , from Hawai‘i, S. (Titanochaeta) sweyzei (Wirth) , comb. nov. from Kaua‘i, Maui, and O‘ahu, and S. (Titanochaeta) vittigera (Hardy) , comb. nov. from Kaua‘i ( Nishida, 2002).

Discussion. The species in this group are infrequently collected and poorly understood taxonomically. The fact that a number of species in the subgenus Titanochaeta are present on multiple, non­adjacent islands suggests that they are either better at dispersing or have a lower rate of speciation than other endemic Hawaiian groups. It also might indicate that there are additional cryptic species remaining to be described in this group.

KEY TO SPECIES OF THE SUBGENUS Titanochaeta Knab

17. Female ovipositor blunt, rounded at apex ........................................ contestata (Hardy)

­ Ovipositor pointed, needle­like ............................................................................…18

18. Crossveins distinctly infuscated; M1 between crossveins dm­cu and r­m short, about 1/5 length of M1 measured from crossvein dm­cu to apex. Maui, O‘ahu, Kaua‘i ......... ................................................................................................................ swezeyi (Wirth)

­ Crossveins not infuscated; M1 between crossveins dm­cu and r­m greater than 1/5 the length of M1 between dm­cu and apex ...................................................................... 19

19. Sides of scutellum with conspicuous setae in addition to anterior and posterior scutellars; both katepisternal setae well developed, roughly subequal in length ................ 20

­ Scutellum lacking secondary setae; length of anterior katepisternal setae variable, ranging from short to subequal setae ................................................................................. 21

20. Mesonotum and scutellum entirely yellow, abdomen predominantly yellow Southern O‘ahu, Hawai‘i, Maui, Moloka‘i, Lana‘i ................................................. bryani (Wirth)

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

21. 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 ... ......................................................................................................... chauliodon (Hardy)

­ Anterior katepisternal not over 1/2 length of posterior, usually small and hair­like; male genitalia not as above; arista with short terminal fork, never long or bifid........ 22

22. 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 ............................................................................................................ vittigera (Hardy)

­ Predominantly black species, mesonotum and scutellum entirely black in ground color, lacking vittae ............................................................................................................. 23

23. First two abdominal segments almost entirely yellow................................................ 24

­ Abdomen almost entirely black, a narrow yellow band may be present at the apex of second tergum ............................................................................................................ 26

24. Tergites three and four shining black, five and six yellow; epandrium about two times longer than high, truncated ventrally; no projection along medial surface of surstylus observed in ventral view. Moloka‘i .......................................... neoevexa O’Grady et al.

­ Abdomen predominantly brown or black; epandrium about two times higher than long, tapered ventrally; moderate to strong projection on medial surface of surstyli when observed in ventral view................................................................................... 25

25. Abdominal tergites four to six brownish yellow on lateral margins, darker on dorsum; male genitalia brownish yellow; pleurae largely brown; surstyli, when observed in lateral view, with sharply pointed projection on mediolateral surface and sharply pointed spine­like process on posterior margin. Hawai‘i ............................ ichneumon (Knab)

­ Abdominal tergites four to six, including genitalia, predominantly shining black; pleurae entirely yellow; surstyli, when observed in lateral view, lacking sharply pointed projection on mediolateral surface, process on posterodorsal surface of surstyli broad, not spine­like and pointed. Kaua‘i .................................. neokauaiensis O’Grady et al.

26. Abdomen shining black beyond second tergite; male genitalia yellow; anterior reclinate inserted near lower 1/3 of fronto­orbital plate. Maui .................... glauca (Hardy)

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

Figures

FIGURE 3. Male terminalia of Scaptomyza (Titanochaeta) chauliodon (Hardy).