Tethysimyia Ebejer, 2009

Ebejer, Martin J., 2023, A first account of Chyromyidae (Diptera: Acalyptratae) from continental Central and South America and some Caribbean Islands, with descriptions of new species, Zootaxa 5319 (3), pp. 301-331 : 312-314

Tethysimyia Ebejer, 2009

Type species: Aphaniosoma deemingi Ebejer, 1996 , by original designation.

With the availability of more material it is now possible to give some more detail on characters of Tethysimyia : fronto-orbital setae usually reduced in size and number or absent, paravertical setulae reduced to a minute size, they can be convergent or divergent, parallel or absent; 1 dorsocentral seta and usually a short one in front of this; acrostichals always in at least 6 rows, usually in 8–10 and somewhat irregular; intrapostalar and prescutellar setae/setulae present; proepisternal seta/setula absent; epandrium small with surstylus fused, aedeagus simple, of uncomplicated structure, with distiphallus more or less straight, weakly sclerotized and mostly translucent; pregonites and postgonites though usually present are often not clearly discernible. The hypandrium is narrow with almost parallel sides and elongated; phallapodeme long rod-like, extending anteriorly in the abdomen. None of the species has the wing veins R 4+5 and M 1 diverging towards the apex of the wing or the complex development of the sternites and gonites typical of Aphaniosoma . In Tethysimyia there is sometimes a row of stronger setulae along the length of the hind tibia, which may end in a longer preapical seta. Species of Tethysimyia differ from Paraphaniosoma Ebejer, 2009 in the broader frons that projects above and in front of the eye, in a more developed facial carina and much broader gena. Paraphaniosoma has a postsutural prealar seta, a more complex male hypopygium with modifications also of the pregenital sternites, and a surstylus articulated with the epandrium. Female Tethysimyia have the paired spermathecae flat and disc-shaped with slight cupping on one side (except in the Arabian species Tethysimyia deemingi Ebejer, 1996 ). Among the species so far examined these structures are relatively uniform. In Aphaniosoma the spermathecae tend to be spherical with only some irregularity on one side. Tethysimyia has some of the smallest species among the Aphaniosominae. The New World species differ from the characters originally described for the Aphaniosominae in the following: the anepisternal seta is placed at the middle of the posterior margin and not on the junction of the upper and middle third; the humeral crossvein is evanescent in most specimens; the dorsal surface of the costa sometimes bears a few spinose setulae as in the Chyromyinae ; some females have mature ova easily seen in a distended abdomen—a feature more typical of the Chyromyinae . These characters suggest that the Neotropical species might belong in another genus, but this will require stronger evidence, examination of more species, and support from molecular studies.

Based on the above characteristics, the species described in Aphaniosoma from Hawaii (Hardy, in Hardy & Delfinado 1980) and the Galapagos (Wheeler, in Wheeler & Sinclair 1994) should be transferred to Tethysimyia . The description of A. aldrichi Wheeler, 1961 includes the following details: “Cheeks very broad, covered with short pale hairs …. One pair of dorsocentrals, acrostichals in about 8 irregular rows …. Wings …. 2L and 3L parallel at tip ….” (2L and 3L refer to veins R 2+3 and R 4+5 respectively). These characters also place A. aldrichi in Tethysimyia . Thus, the following new combinations are proposed: Tethysimyia aldrichi ( Wheeler, 1961) comb. nov., Tethysimyia macalpinei ( Hardy, 1980) comb. nov., Tethysimyia minuta ( Hardy, 1980) comb. nov., Tethysimyia arenicola ( Wheeler, 1994) comb. nov., Tethysimyia galamarilla ( Wheeler, 1994) comb. nov. and Tethysimyia rabida ( Wheeler, 1994) comb. nov.

Wheeler & Sinclair (1994) illustrated the terminalia of the three species they described. Their interpretation of some structures differs from that of this author. In their figures, the structure depicted as arising equally from the caudal end of the hypandrium as it is from the anteroventral part of the epandrium is labelled as surstylus, but this is more likely to be the pregonite and their bacilliform sclerite the postgonite. Their figures also depict the long phallapodeme and hypandrium as in the new species here described.

Key to Central and South American species of Tethysimyia , including the Oceanian species from Hawaii. T. aldrichi is excluded as no material has been seen to examine it for detail missing from the description.

1 Head longer than high; frons not projecting; eye long oval, long diameter about twice length of short diameter; wing veins R 4+5 and M 1 parallel to apex of wing....................................................... chilensis sp. nov. ( Chile)

- Head spherical, or a little higher than long; frons projecting beyond eye margin above and anteriorly; eye short oval with long diameter only about 1.3 times as long as short diameter; wing veins R 4+5 and M 1 convergent towards apex of wing, sometimes only slightly so...................................................................................... 2

2 Frontal setulae reclinate; scutum grey anteriorly; acrostichals in 8–10 rows; abdominal tergites grey with pale posterior margins.................................................................... arenicola Wheeler ( Ecuador, Galapagos)

- Frontal setulae proclinate; scutum yellow; acrostichals in 6–8 rows; abdominal tergites yellow, at most with narrow, pale brown bands anterodorsally.................................................................................. 3

3 Males .............................................................................................. 4

- Females............................................................................................ 9

4 Frons, face and basal flagellomere black ( Fig. 15 )................................. nigrifacies sp. nov. (West Indies)

– Frons, face and basal flagellomere yellow................................................................. 5

5 Hind basitarsus distinctly modified: broad and flattened dorsoventrally; hind tibia with prominent anterior setae minuta Hardy (Hawaii) & galamarilla Wheeler (Galapagos) ................(distinguishable by the characters in the male hypopygium)

- Hind basitarsus not modified; tibia without prominent anterior setae............................................. 6

6 Mediotergite black; scutum usually with pale brown vittae; abdominal tergites dark shiny brown with narrow pale hind margins; eyes with microtrichia between every 1 or 2 ommatidia........ litophila sp. nov. (Pacific coasts of Costa Rica and Mexico)

- Without the above combination of characters............................................................... 7

7 Paravertical setulae present; acrostichals in 6–8 rows.................................. rabida Wheeler (Galapagos)

- Paravertical setulae absent; acrostichals in 8–10 rows........................................................ 8

8 acrostichals in 10 rows at level of transverse scutal suture................................ macalpinei Hardy (Hawaii)

- acrostichals in 8 rows at level of transverse scutal suture............................... bonairensi s sp. nov. ( Bonaire)

9 Paravertical setulae absent ( Fig. 19A ).................................................................... 10

- Paravertical setulae present............................................................................ 11

10 Entirely yellow species........................................................ bonairensis sp. nov. ( Bonaire)

- Brown transverse bands present on abdominal tergites 3 and 4; lateral spots present on abdominal tergites 2, 5, 6 ( Fig. 20A )........................................................................... undescribed species A ( Bonaire)

11 3 reclinate fronto-orbital setae; tibia and tarsus of anterior and middle leg pale brown; abdominal tergites with narrow dark bands on segments 2–6, and segments 3–5 with dark spot or a widening at midpoint of band ( Fig. 20C )........................................................................................... undescribed species C ( Bonaire)

- 2 reclinate fronto-orbital setae; legs all yellow; abdominal tergite with different pattern if bands are present............ 12

12 Mediotergite yellow; anterior declivity of scutum yellow; abdomen with transverse bands on tergites 1–5, if present, at most pale brown; tergite 6 with pair of small pale brown spots; eyes bare.................... nigrifacies sp. nov. (West Indies) ( macalpinei Hardy (Hawaii) , minuta Hardy (Hawaii) , galamarilla (Wheeler) (Galapagos) , rabida (Wheeler) (Galapagos) and undescribed species D ( French Guiana) are not reliably distinguished at present in the female sex.)

- Mediotergite black; anterior declivity of scutum with dark patch............................................... 13

13 Abdomen with broad dark brown transverse bands on tergites 1–5; tergite 6 with pair of large brown spots ( Fig. 13 ); eyes with microtrichia between every 1 or 2 ommatidia................ litophila sp. nov. (Pacific coasts of Costa Rica and Mexico)

- Abdomen with narrow brown transverse bands on abdominal tergites 3–5; tergites 2 and 6 with small lateral spots ( Fig. 20B ); eyes bare................................................................... undescribed species B ( Bonaire)

Figures

FIGURE 13. Tethysimyia litophila sp. nov,. A. holotype, male. B. same head dorsal view. C. same, hypopygium in situ, posterior view. D. paratype, female, abdomen, posterodorsal view.

FIGURE 15. Tethysimyia nigrifacies sp. nov., holotype, male. A. habitus, lateral view. B. dorsal oblique view. C. head, anterolateral view. D. same, dorsal view.

FIGURE 19. Tethysimyia spp. females, A. species A, head, posterolateral view, scale bar = 0.25mm. B. same species (another specimen), lateral view. C. species C, head, lateral view.

FIGURE 20. Tethysimyia spp. female specimens from Bonaire, A. species A. B. species B. C. species C.