Key to the Adult Forcipomyia (Metaforcipomyia) of Costa Rica

Adults of the subgenus Forcipomyia (Metaforcipomyia) may be distinguished from those of other New World Forcipomyia by the absence of a row of slender spicules that comprise the comb at the apex of the hind tibia. In addition, the males of all species have antennal flagellomeres 5–8 fused, a condition not present in any other subgenus of Forcipomyia .

Females of the following species are unknown: F. (M.) rivalis n. sp., F. (M.) truncata n. sp., F. (M.) atenasensis n. sp., F. (M.) osaensis n. sp., F. (M.) grandiseta n. sp., F. (M.) longiflagellata n. sp., F. (M.) macroseta n. sp., F. (M.) germinata n. sp., and F. (M.) ronderosae n. sp.

1. Male............................................................................................... 2

- Female............................................................................................ 17

2. Parameres present (Figs. 50, 55, 60, 65, 75, 85, 95, 100, 110); hind tarsal ratio 1.75–2.50............................. 3

- Parameres absent (Figs. 6, 15, 22, 29, 38, 44); hind tarsal ratio 0.75–1.25........................................ 12

3. Foretarsomere 2 with 2–4 thick, basally reinforced setae, similar to those forming a row on tarsomere 1 (Fig. 48)......... 4

- Foretarsomere 2 without thick, basally reinforced setae....................................................... 6

4. Flagellomere 10 proportionally short (1.10–1.35 X longer than flagellomere 11) (Fig. 46)................ grandiseta n sp.

- Flagellomere 10 proportionally elongate (2.07–2.80 X longer than flagellomere 11)................................. 5

5. Flagellomere 10 2.60–2.80 X longer than flagellomere 11 (Fig. 52); wing without pattern; aedeagus quadrate, truncate apically (Fig. 56)............................................................................ longiflagellata n. sp.

- Flagellomere 10 2.07 X longer than flagellomere 11 (Fig. 57); wing patterned (Fig. 113); aedeagus tapering apically to rounded apex (Fig. 61)............................................................................ macroseta n. sp.

6. Wing patterned, with a dark patch on anterior margin of wing distal to apex of the radial cells and the apices of at least each of M2, CuA1 and CuA2 (Figs. 114–119)...................................................................... 7

- Wing without pattern of spots on apices of veins, with at most a dark patch on anterior margin of wing, distal to apex of radial cells (Figs. 5, 14, 21, 43).............................................................................. 12

7. Tarsomere 1 of hind leg brown, contrasting with pale tarsomeres 2–5............................................ 8

- Tarsomeres of hind leg either unicolourous or with pattern of contrasting pigmentation.............................. 9

8. Flagellomeres 3–9 pale (plume arising from these is pale) (Fig. 82); aedeagus slender, with apical lobes short, separated by broad rounded gap (Fig. 86)................................................................ albipluma n. sp.

- Flagellomeres 3–9 light to dark brown (plume arising from these is brown) (Fig. 72); aedeagus stout, with apical lobes well developed, more elongate, separated by narrow gap (Fig. 76)......................................... rursa n. sp.

9. Tarsomeres of hind leg without contrasting pigmentation between any two tarsomeres, although the tarsomeres 1– 5 may be progressively lighter................................................................... pseudocerifera n. sp.

- Tarsomere 1–2 of hind leg brown, contrasting with pale tarsomeres 3–5......................................... 10

10. Apex of aedeagus with short apicomedial prong (Fig. 96)........................................ germinata n. sp.

- Apex of aedeagus without apicomedial prong (Figs. 101, 111)................................................. 11

11. Aedeagus triangular, tapering distally (Fig. 101)................................................... heroni n. sp.

- Aedeagus shield-shaped with lateral subapical, heavily sclerotized projections directed laterally, apex concave (Fig. 111)........................................................................................... ronderosae n. sp.

12. Aedeagus without elongate, posteriorly directed prong............................................. osaensis n. sp.

- Aedeagus with elongate, slender posteriorly directed prong................................................... 13

13. Labrum truncate apically, with transverse row of elongate spicules (Fig. 3); scutum pale, contrasting with dark scutellum, or, with dark pigmentation, equal to that of scutellum.......................................................... 14

- Labrum tapering apically, without transverse row of elongate spicules (Fig. 26); scutum pale, contrasting with dark scutellum................................................................................................... 16

14. Hind femur with at least basal 0.3 darkly pigmented, apical portion pale (Fig. 4); pigmentation of scutum variable: pale, with patch of darker pigmentation anteriorly, more extensively partially pigmented or entirely darkly pigmented..................................................................................................... pluvialis Malloch

- Hind femur uniformly pale or uniformly dark (Figs. 13, 20); scutum entirely pale or with uniformly dark pigmentation.... 15

15. Hind femur uniformly pale (Fig. 13); scutum pale, contrasting with dark scutellum; basal arch of aedeagus heavily sclerotized, extending 1/20 of total length.................................................................. rivalis n. sp.

- Hind femur uniformly dark (Fig. 20); scutum and scutellum with uniformly dark pigmentation; basal arch of aedeagus poorly sclerotized, extending to 1/10 of total length..................................................... truncata n. sp.

16. Hind femur with broad basal dark band, and all tibiae with subbasal and apical dark bands (Fig. 27).......... anniae n. sp.

- Hind femur basally brown and at least ¼ apical pale, and all tibiae with base broadly paler than apical portion (Fig. 36)........................................................................................... atenasensis n. sp.

17. Hind tibia entirely dark brown.......................................................................... 18

- Hind tibia mostly pale, apex dark........................................................................ 21

18. Cercus pale or very light brown, contrasting with dark segments 8–9.................................. heroni n. sp.

- Cercus brown, similar to dark segments 8–9............................................................... 19

19. Largest spermatheca more or less spherical (Fig. 91); flagellomeres 3–8 paler than others (Fig. 87)....... albipluma n. sp.

- Largest spermatheca elongate (Figs. 71, 81); flagellomeres uniformly brown (Figs. 67, 77).......................... 20

20. Spermathecae slightly unequal in size (Fig. 71); proximal flagellomeres flasked-shaped (Fig. 67)..... pseudocerifera n. sp.

- Spermathecae unequal in size (Fig. 81); proximal flagellomeres bottle-shaped (Fig. 77).................... rursa n. sp.

21. Each tibia with subbasal and apical band of dark pigmentation....................................... anniae n. sp.

- Each tibia with, at most, dark pigmentation at apex............................................ pluvialis Malloch