Key to Mesoamerican and Caribbean Male Mesorhaga

Accurate identification of Mesorhaga may require clearing the hypopygium, since subtle but distinct cercal differences are often used to separate related species.

1. Wing vein M with distinct curved, almost right angle bend (Fig. 1 c); wing sometimes with brown cloud in both sexes, but even then can be faint ( lacrymans group)...........................................................................2

-. Wing vein M with more gentle curve (e.g. Fig. 3 d); wing hyaline in both sexes ........................................ 5

2. Halter mostly yellow, with infuscated club; distal quarter of femora I and II and all tibiae yellow; hypopygium (Fig.1 e) (Costa Rica) ............................................................................................. M. sarukhani n. sp.

-. Halter brown to black; femora dark almost entirely dark brown to black; other characters variable........3

3. Legs entirely dark brown to black; It5 (Fig. 1 b) expanded and flattened, subtriangular, with long dorsal setae and expanded pulvilli (MSSC); hypopygium (Fig.1 a)(Costa Rica & Panama) M. lacrymans Parent

-. Tibiae and basitarsi I and II yellowish; It5 only slightly expanded or unmodified......................................4

4. Ventral postcranium with abundant black setae; lateral scutellar setae about half as long as median setae; femora with av and pv setae entirely black; TI distally and It1–2 with posterior row of long setae; dm-cu crossvein distinctly longer than distal section of CuA1; distal CuA1 straight; hypopygium (Fig.1 d) (Costa Rica) ..................................................................................................................................... M. cocori n. sp.

-. Ventral postcranium with abundant white setae; lateral scutellar setae about two thirds length of median setae; femora with av and pv setae, white on basal third to half, black distally; TI with pd row of brownish setae along length, with 4 -5 slightly longer black setae spaced among them; dm-cu crossvein distinctly shorter than distal section of CuA1; distal CuA1 slightly curved towards wing apex; hypopygium (Fig. 1 g) (Costa Rica) ............................................................................................................................. M. hule n. sp.

5. Tarsus of leg I (Fig. 3 c): It2 with 6–7 black, ventral, spinelike setae, It3 very short, and It4 with 4 short ventral setae (MSSC); lateral frons and ocellar tubercle with supernumerary setae; lower calypter with long white setae (black in female) ( isthmia group) ........................................................................................... 6

-. Tarsus of leg I ventrally bare, with It3 usually longer than It4; lateral frons and ocellar tubercle with characteristic setation, lacking extra setae; lower calypter various........................................................................7

6. Femora mostly dark brown, with metallic green reflections; IIIt4–5 flattened, ventrally pad-like; hypopygium (Fig.3 a) with cercus massive and straight, distally clavate, with strong spinelike setae (Veracruz,

Mexico to Panama) ............................................................................................................. M. isthmia n.sp. -. Femora and tibiae mostly yellow; IIIt4–5 not flattened (Cuba) ................................. M. ornatipes Va n D u z ee

7. Claws and/or pulvilli of tarsus I distinctly longer than those of legs II and III...........................................8

‒• Claws and pulvilli of all tarsi short, subequal and unmodified ...................................................................9

8. Posterior claw of leg I (Fig. 2 c) greatly enlarged and curved; tibia II bare of major setae; halter black; hypopygium (Fig. 2 b) (southern Mexico) .................................................................. M. falciunguis n. sp.

-. Both claws of leg I enlarged, and distinctly longer than those of legs II and III; tibia II with strong ad and pd setae; halter with yellow club; hypopygium (Fig. 3 e) (Costa Rica) ......................... M. baadsvicki n. sp.

9. Halter yellow.............................................................................................................................................10

-. Halter brown to black .................................................................................................................................11

10. All femora black with yellow knees; It1 long, distinctly longer than It2-5 combined; hypopygium (Fig. 2 d): cercus with outer apical notch (Costa Rica) .................................................................. M. villanuevi n. sp.

-. All femora entirely yellow; It1 subequal to It2-5 combined; hypopygium (Fig. 4 b): cercus entire, without outer notch (southern Mexico) .................................................................................... M. nayaritensis n. sp.

11. Ventral postcranium with abundant white setae; wing unusually broad, almost half as wide as long; hypopygium (Fig. 3 f) hypandrium with hood; cercus curved and apically clavate, with elongate subapical setae (Morelos, Mexico) .................................................................................... Mesorhaga mexicana n. sp.

-. Ventral postcranium with abundant black setae; wing width distinctly less than half wing length ........ 12

12. Femur I brown, with long, dark brownish ventral and pv hairs along length; hypopygium (Fig. 2 a): cercus curved with apical tuft of setae on subrectangular projection (Guatemala) .......... M. adunca (Van Duzee) .

-. Femur I yellow, with only short, ventral hairs; hypopygium (Fig.4 a); cercus distally expanded, with group of strong, distal setae (Veracruz, Mexico). ...................................................... Mesorhaga minatitlan n. sp.