1	Abdomen to naked eye appearing black when viewed from above, if tomentum present, bronze or brown but not gold, densely covered in strong abdominal setae, resembling Leschenaultia Robineau-Desvoidy in general appearance (Figs 76, 93); 3–5+ pairs of marginal setae on both ST1+2 and T3	2
–	Abdomen either black with contrasting tomentose bands more striking, “typical” Belvosia, or with a more ochraceous ground color; not entirely black. Setation of abdomen restricted to marginal setae (Figs 19, 61)	3
2	Tergite 5 when viewed under certain angles of light, completely dull golden tomentose; basicosta yellow; setulae of genal dilation and pleura mostly pale; species only known from 1000m elevation and above	B.minorcarmonai sp. n.
–	Tergite 5 black, shiny, with very inconspicuous and very sparse tomentum; basicosta mostly black; setulae of genal dilation and pleura black	B.rostermoragai sp. n.
3	Abdominal bands of T4 and T5 both with deep orange to brick red tomentum	4
–	Abdominal bands of T4 and T5, when present either with bronze-gold or white tomentum	5
4	Pollen of head brown except facial ridges and a spot on parafacial, where it is silvery	B.vanderwulpi Williston
–	Pollen of head silvery white, palpus dark brown almost black, facial ridge with setulae extending almost along entire length, pedicel and postpedicel concolorous black	B.ferruginosa Townsend
5	Basicosta brilliant yellow-red/orange; general appearance variable, but frequently not black with yellowish tomentose bands	6
–	Basicosta partly black/dark brown; often characterized as large black flies with yellow tomentose bands on abdomen	28
6	Abdomen with light ground color (yellow-orange), occasionally this orange only apparent when viewed laterally especially in photos; often male wth proclinate orbital setae present	7
–	Abdomen with dark ground color (can be dark yellow-orange appearing black to the naked eye), either with or without a narrow black median stripe or indistinct stripe created by tomentum; males without proclinate orbital setae	11
7	Dorsum of thorax gray tomentose	8
–	Dorsum of thorax ranging from entirely bronze to gold tomentose concolorous with T3–T5	10
8	Abdomen entirely light orange ground color, postocular margins gold tomentose	B.ricardocaleroi sp. n.
–	Abdomen light orange ground color, darkened dorsally; postocular margins silver–gray tomentose	9
9	Postpedicel orange concolorous with pedicel; wing orange infuscate basally; T3 with light dusting of gold tomentum medially bisected by a thick stripe extending through T4	B.equinoctalis (Townsend)
–	Postpedicel dark with orange basally, juxtaposed against a yellow pedicel; wing brown-yellow infuscate basally; T3 with gold tomentum only along anterior margin, stripe bisecting tomentosity almost indistinct	B.obesula (Wulp)
10	Four pairs of scutellar marginal setae; calypters orange translucent; middorsal abdominal stripe occluded by bronze tomentum of abdomen	B.mira Reinhard
–	Three pairs of scutellar marginal setae; calypters pale yellow translucent; middorsal abdominal stripe visible through gold tomentum of abdomen	B.ochriventris (Wulp)
11	Median marginal setae extremely weak–absent from Syntergite 1+2 (ST1+2)	12
–	Median marginal setae present on ST1+2	17
12	Both calypters white translucent	13
–	Both calypters heavily infuscate reddish/brown (From ACG, parasitizing Notodontidae exclusively)	14
13	Fronto-orbital plate, parafacial and thorax silver tomentose, calypters white translucent throughout	B.omissa Aldrich
–	Fronto-orbital plate, parafacial and thorax gold tomentose, calypters white on edges with brown centrally	B.manuelriosi sp. n.
14	Median marginal setae absent from tergite 3; fronto-orbital plate with setulae extending well below lower margin of pedicel	B.ruthfrancoae sp. n.
–	Median marginal setae present on tergite 3, at most 3–4 fronto-orbital setulae present below lower margin of pedicel	15
15	Dorsal surfaces of scutum tawny tomentose, transitioning to brown postsuturally; pedicel orange constrasting with postpedicel	B.matamorosa Reinhard
–	Dorsal surfaces of scutum entirely silver tomentose; pedicel brown concolorous with postpedicel	16
16	T4 with gold tomentum only on anterior 60% of tergite with a middorsal stripe bisecting tomentosity	B.manuelpereirai sp. n.
–	T4 and T5 entirely brilliant gold tomentose	B.recticornis Macquart
17	Pilosity of gena, anepisternum, katepisternum completely dark	18
–	Pilosity of gena, anepisternum, katepisternum partly pale, particularly posterior to row of major setae along posterior margin	23
18	Tergite 4 completely devoid of any gold tomentum	19
–	Tergite 4 bearing at least 10% gold/bronze tomentum	20
19	Arista orange, abdomen black ground color throughout, wings orange basally	B.naccina Reinhard
–	Arista black, abdomen orange-brown ground color appearing black on T3, wings evenly infuscate throughout	B.sergioriosi sp. n.
20	Median Marginal Setae (MMST) ST1+2 weak, but distinctly present ; T5 gold tomentose with a very sparse and randomly spaced vestiture of short black setulae present lateroventrally	B.carolinacanoae sp. n.
–	MMST ST1+2, distinctly present and strong; T5 gold tomentose with a randomly spaced vestiture of short black setulae present on all surfaces	21
21	Anterior margin of T3 devoid of gold tomentum; gold tomentum on T4 90% coverage of tergite, only part not tomentose is a narrow band adjancent to marginal setae, tergal band complete with no longitudinal stripe, or if stripe apparent then only as a slight darkening less than thickness of one median marginal seta	B.ansata Reinhard
–	Anterior margin of T3 bearing some minor gold tomentum <10%; gold tomentum on T4 ranging from 20–40% coverage of tergite, tergal band bissected medially by a dark longitudinal stripe	22
22	Gold tomentum on T5 covering entire tergite inclusive of tergal margin; epandrium orange	B.ciliata Aldrich
–	Gold tomentum on T5 interrupted along dorsomedial apex, replaced with a small but presente darkened spot; epandrium black,	B.anacarballoae sp. n.
23	Fronto-orbital plate, appearing glabrous yellow; both calypters pale white translucent	24
–	Fronto-orbital plate, not as above, ranging from brilliant gold to dull gray tomentose	25
24	Gena concolorous with fronto-orbital plate usually appearing glabrous yellow; calypters white overall; abdominal tergite 5 completely orangish yellow with similarly colored tomentum that contrasts with tomentum of other segments; majority of hair-like setulae on genal dilation black; wings only slightly infuscate	B.unifasciata (Robineau-Desvoidy)
–	Gena brilliant silver tomentose with fronto-orbital plate usually appearing glabrous yellow; calypters white with yellow-orange fringe; abdominal tergite 5 black in ground color, with pale tomentum that is similar to tomentum of other segments; tomentum sparse to absent on posterior margin so that it appears black; majority of hair-like setulae on genal dilation pale; wings dark brown infuscate	B.slossonae Coquillett
25	Katepisternum, meron, and anepimeron bearing only long pale setulae; in males fronto-orbital plate and up to 50% of parafacial gold tomentose; females dull gray tomentum on fronto-orbital plate, and silver parafacial; female palpus apically clubbed and covered in a sparse vestiture of setulae	B.brigittevilchezae sp. n.
–	Katepisternum, meron, and anepimeron with mostly black-brown setulae with few long pale setulae interspersed; both males and females without gold tomentum on either fronto-orbital plate or parafacial (sometimes tomentum can be thin so as to make the head appear yellow but distinctly not gold tomentose)	26
26	T4 almost devoid of gold tomentum with a narrow fringe of bronze-gold tomentum apparent only along anterior margin of tergite	B.angelhernandezi sp. n.
–	T4 with gold tomentum covering over 50% of tergite, broken medially by narrow black band	27
27	Setulae below lowest frontal seta dark; four postsutural acrostichals	B.adrianguadamuzi sp. n.
–	Setulae below lowest frontal seta pale yellow; three postsutural acrostichals	B.calixtomoragai sp. n.
28	Abdominal tergite 5 entirely gold or white tomentose, sometimes with at most a vague dark stripe dorsally	29
–	Abdominal tergite 5 with tomentum posterior to large marginal setae absent, thus appearing black apically	32
29	Abdomial tergite 4 entirely black, devoid of gold tomentum	B.desita (Walker)
–	Abdomial tergite 4 gold tomentose	30
30	Gold tomentum on T4 covering entire tergite, not bisected medially by a dark strip so that both T4 and T5 are uninterrupted gold tomentose	B.semiflava Aldrich
–	Gold tomentum on T4 covering at most 50% of tergite, bisected medially by a dark strip so that two distinct tomentose patches on T4 appear separated from T5	31
31	Abdomen slightly flattened more like the 'regular' Belvosia, T5 slightly open vaguely exposing the genital capsule; T5 entirely gold with a slight blackening around median pair of marginal setae; fronto-orbital plate with a pale gold bronze tomentum	B.canalis Aldrich
–	Abdomen rounded globose, T5 with only a slit operculum enclosing the genital capsule; T5 entirely gold lacking any black around median pair of marginal setae; fronto-orbital plate with silver-gray	B.osvaldoespinozai sp. n.
32	Both calypters appearing whitish with a pale fringe of setulae	33
–	At least upper calypter, and frequently both, dark, often with a dark fringe	35
33	Anterodorsal row of setae on hind tibia fringelike, formed by a very regular row of uniformly sized setae separated from each other by less than the width of their sockets; antennae short, postpedicel about 2X as long as pedicel; all major abdominal setae rather strongly appressed and directed posteriorly; MMST absent from ST1+2 and reduced frequently absent on ST3	B.gloriasihezarae sp. n.
–	Anterodorsal row of setae on hind tibia irregular and not fringelike, usually with several median setae that are distinctly longer than others; antennae, postpedicel greater than 2X as long as pedicel; all major abdominal setae not strongly appressed; often MMST present both ST1+2 and present on ST3	34
34	Setae on facial ridge weak, each seta less than length of antennal pedicel; anepimeron with some obviously pale setulae, especially below and posterior to major anipemeral setae; tomentum on male fronto-orbital plate yellow-gold	B.townsendi Aldrich
–	Setae on facial ridge strong, each seta as long as or longer than length of antennal pedicel; anepimeron with entirely dark setulae, rarely with a few pale setulae; tomentum on male fronto-orbital plate silvery-white	B.argentifrons Aldrich
35	Lower calypter pale in color, contrasting to the upper calypter strongly infuscate	36
–	Lower calypter dark, concolorous with upper calypter	37
36	Golden tomentum reaching hind margin of abdominal tergite 4 laterally and ventrally, so the hind margin does not appear to have a uniformly dark band; surstylus nearly straight, not distinctly arcuate	B.canadensis Curran
–	Golden tomentum not reaching hind margin of abdominal tergite 4 laterally and ventrally, so the hind margin appears to have a uniformly dark band; surstylus distinctly arcuate anteriorly	B.bifasciata (Fabricius)
37	Post sutural surface of scutum displaying mostly brassy brown tomentum, concolorous with tomentosity of scutellum (visible under certain angles of light), or glabrous devoid of tomentosity	38
–	Post sutural surface of scutum displaying mostly silver tomentum, contrasting with tomentosity of scutellum (visible under certain angles of light), if any brassy tomentum present then this confined to postalar callus	40
38	Thorax appearing glabrous and devoid of tomentum	B.splendens Curran
–	Thorax tomentose	38
39	Palpus apically orange, darkened basally	B.eldaarayae sp. n.
–	Palpus brown throughout	B.auratilis Reinhard.
40	With at most most a narrow fringe of gold on T4, occupying less than 10% of tergite, males most often lacking gold tomentum on T4 entirely; postpedicel only up to maximum 2X as long as pedicel	41
–	T4 with gold tomentum covering at least 10% or more of tergite either as a solid unbroken band or bisected medially by darker brassy-brown tomentum; postpedicel variable length	44
41	Median marginal setae on ST1+2 reduced, if female then median marginal setae absent from tergite; anterodorsal setae on hind tibia regular and comblike, typically at most 1.25X as long as width of supporting tibia, each seta separated from the other with regular spacing no more than the width of the base of the preceding seta	B.freddyquesadai sp. n.
–	Both males and females with strong median marginal setae on ST1+2; anterodorsal setae on hind tibia irregular, not comblike, many seta exceeding 1.25X as long as width of supporting tibia, setae irregularly spaced	42
42	Pedicel orange to reddish brown, contrasting the dark blackened color of the postpedicel; postpedicel greater than 2X length of pedicel	B.petronariosae sp. n.
–	Pedicel black to dark brown, not contrasting the dark blackened color of the postpedicel; postpedicel at most 2X length of pedicel	43
43	Gena 1/3 length of eye; postpedicel 2X length of pedicel; inner row of 5-10 setae anterior to postocular setae; T5 with a sparse vestiture of setulae on dorsal and ventral surfaces	B.duniagarciae sp. n.
–	Gena 1/2 length of eye; postpedicel 1.5X length of pedicel; lacking an inner row of 5-10 setae anterior to postocular setae; T5 devoid of any setulae along dorsal surface outside of those surrounding tergal marginal setae	B.robertoespinozai sp. n.
44	Parafacial setulae yellow	B.pabloumanai sp. n.
–	Parafacial setulae dark	45
45	Anterodorsal setae on hind tibia irregular, not comblike, many seta exceeding 1.25X as long as width of supporting tibia, setae irregularly spaced	46
–	Anterodorsal setae on hind tibia regular and comblike, typically at most 1.25X as long as width of supporting tibia, each seta separated from the other with regular spacing no more than the width of the base of the preceding seta	53
46	Palpus dark umber brown throughout	B.borealis Aldrich
–	Palpus with at least partial yellow-orange	47
47	Gold tomentosity on T4 occupying over 60% of tergite, typically with only a narrow margin of bare tergite visible surrounding the marginal setae	48
–	Gold tomentosity on T4 reduced, occupying up to maximum 50% of tergite, often males with T4 mostly black	51
48	Postpedicel short, less than 1.5 times length of pedicel (typically almost equal to length of pedicel)	B.bicincta Robineau-Desvoidy
–	Postpedicel longer, more than 2X times length of pedicel (typically 3–4X)	49
49	Cercus narrow and parallel sided, apically beaked with a small indentation apically, slight swelling directly adjacent to this indentation, surstylus narrow, parallel sided, digitiform (Fig. 41a); females with rounded end to palpus with setulae extending apically; specialists reared only from Sphingidae	B.eliethcantillanoae sp. n.
–	Cercus not as descirbed above, surstylus oar-shaped, either with a slight pinch medially along ventral edge or a straight (Figs 67a, 70a); females: palpus more sharply pointed and bare apically; specialist feeding only on a variety of Saturniidae; specialist reared only from Saturniidae	50
50	Fronto-orbital plate silver with varying tonality of gold tomentum (ranging from very yellow-gold to silver with brassy tones), darkening slightly apically in some cases appearing glabrous or void of tomentum apically, in females uniformly silver gray with darkened area much larger and shinier; surstylus shorter than cercus, inversely tapered, spatulate, apically rounded with more curvature along upper edge; female antenna short of facial margin by 1.5X length of pedicel, underside of T3 silver tomentose along anterior margin; specialist feeding only on Saturniidae (Eacles sp.)	B.keinoraragoni sp. n.
–	Fronto-orbital plate silver tomentose, darkening apically in some cases appearing glabrous or void of tomentum apically, in females darkened area much larger and shinier; surstylus subequal in length to cercus, parallel-sided, apically rounded; female antenna short of facial margin by 1X length of pedicel, entire surface of T3 uniformly lightly brown rusty tomentose including underside (apparent under certain angles of light); specialist feeding only on Saturniidae (Citheronia sp.)	B.luciariosae sp. n.
51	Setae at base of scutum strong and irregularly spaced not appearing as a regularly formed marginal row; males with postpedicel short 2/5X as long as pedicel; abdominal tergite T3 with devoid of gold tomentum directly adjacent to ST1+2	B.duvalierbricenoi sp. n.
–	Setae at base of scutum strong and regularly spaced appearing as a regularly formed marginal row; males with postpedicel long 1/4–1/3 as long as pedicel;abdominal tergite T3 with traces of gold tomentum directly adjacent to ST1+2	52
52	Male, fronto-orbital plate gold; at most 1–2 small setae anterior to postocular row; gold wrapping around T4 extending to underside; cerci when viewed dorsally, regularly tapered with no distinct triangle apically, when viewed laterally only vaguely hirsute, surstylus slightly widened basally with a slight curvature; lobes of ST5 2.4x as long as basal section; female, with at most a row of 3–5 small setae anterior to postocular row	B.diniamartinezae sp. n.
–	Male, fronto-orbital plate mostly gray only with hints of gold present; row of 5–7 small setae anterior to postocular row; gold wrapping around T4 extending 3/4 around tergite not reaching underside; cerci when viewed dorsally, basal 3/5 widened, apical 2/5 equilaterally triangular and pointed, when viewed laterally strongly hirsute basally, surstylus equilaterally sided and straight with no distict curvature; lobes of ST5 1.75x as long as basal section; female, with row of 5–8 small setae anterior to postocular row	B.ciriloumanai sp. n.
53	Unsclerotized "window" at base of ST5 vaguely rectangular/ovoid with no distinct curvature at apices as in Figs 59c, 65c; when viewed laterally surstylus thickening at midpoint, basally thickened	54
–	Unsclerotized "window" at base of ST5 vaguely curved at apices	55
54	When viewed posteriorly cerci form a sharply pointed wide base triangle, with sides curving slightly inward, length to tips 1.3X basal width	B.joseperezi sp. n.
–	When viewed posteriorly cerci form a sharply pointed triangle with a narrow base, sides straight, length to tips 1.8X basal width	B.jorgehernandezi sp. n.
55	Surstylus when viewed laterally rounded at apices	56
–	Surstylus when viewed laterally pointed at apices	57
56	Epandrium and hypandrium not densely hirsute; when viewed laterally surstylus subequal in legth to cerci; surstylus apically rounded with a slight anterior curve along inferior edge, giving the process a digitiform appearance	B.guillermopererai sp. n.
–	Epandrium and hypandrium densely hirsute; when viewed laterally surstylus distinctly shorter than cerci; cerci apically rounded flat along inferior edge, giving the process a dull blade like appearance	B.harryramirezi sp. n.
57	Cerci when viewed laterally with posterior edge evidently straight ending in a curved tip; surstylus flat along anterior edge, posterior edge curved, as in an inverted straight back blade shape	B.hazelcambroneroae sp. n.
–	Cerci when viewed laterally with posterior edge rounded ending in a curved tip; surstylus angled upwards from anterior edge, upward edge curved, giving it a spear type point	B.josecortezi sp. n.

This key was written based on characters present in both males and females, in some rare cases where sexual dimorphism is present the species have been divided into parts and the sexes indicated. The geographic boundaries include Canada, south to the Panama border with Colombia. This key illustrates the identifying characters states for 33 new species from Area de Conservación Guanacaste along with 25 previously described species from North- and Meso-America.