1.
 Posterior sternite emarginate at apex (males)
 

1'.

 Posterior sternite rounded at apex (females)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
2 (1).
 Elytra with vestiture
 

2'.

 Elytra without vestiture
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
3 (2).
 Anterior tibia arcuate (Fig. 1).
 

3'.

 Anterior tibia straight (Fig. 2).
Fig. 1. M. nogueirai
arcuate foretibia
Fig. 2. M. mars
straight foretibia
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
4 (3).
.
 Anterior angles of pronotum produced into antero-laterally projecting horns (Fig. 3).
 

4'.
.
.

 Anterior angles of pronotum produced into laterally projecting horns (Fig. 4). Southwestern Mexico (Sierra Madre Occidental)
M. occidentale
Bolívar y Pieltain, Jiménez-Asúa, and Martínez
Fig. 3. M. elephas
pronotum produced into antero-laterally
projecting horns.
Fig. 4. M. occidentalis
pronotum produced into laterally
projecting horns.

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5 (4).
.
.
.
 Apices of anterior angles (horn) of pronotum curving inward (Fig. 5). Side of elytron, behind humerus with short, recumbent setae. Mexico (southern Sinaloa: Pacific slopes of Sierra Madre Occidental)
.
.
M. nogueirai (Morón)
 

5'.
.
.

 Apices of anterior angles (horns) of pronotum not curving inward (Fig. 6). Side of elytron, behind humerus velutinous (short, erect setae). Southern Mexico to Venezuela
.
M. elephas (Fabricius)
Fig. 5. M. nogueirai
apices of pronotal horns curving inwards
Fig. 6. M. elephas
apices of pronotal horns not curving inwards
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
6 (3').
Elytra velutinous (short, erect setae)
 

6'.

 Elytra pilose
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
7 (6).
.		 Mid-prothoracic horn narrowly emarginate at apex. Anterior angles of pronotum produced into elongate, acute horns (Fig. 7). Brazil
M. gyas Herbst
 

7'.
.

 Mid-prothoracic horn broadly-bifurcate at apex. Anterior angles of pronotum produced into short, acute horns (Fig. 8). Brazil
M. anubis Chevr.
Fig. 7. M. gyas median pronotal horn narrowly emarginate at apex, anterior angles of pronotum produced into elongate, acute horns.

Fig. 8. M. anubis median pronotal horn broadly-bifurcate at apex, anterior angles of pronotum produced into short, acute horns.

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
8 (6').
.
 Anterior margin of clypeus with acute, spiniform teeth seperated by 3 tooth widths or more
 

8'.
.

 Anterior margin of clypeus with acute, spiniform teeth seperated by 1 tooth width or less. Argentina and Paraguay
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
9 (8).
 Pronotum with median, anteriorly directed horn
 

9'.
.

 Pronotum without median, anteriorly directed horn. Mexico (central Baja California: Cedros Island)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
10 (9).
.
 Distance between apices of anterior angles (horns) of pronotum nearly twice width of head (Fig. 9). Mexico (southern Baja California)
 

10'.
.

 Distance between apices of anterior angles (horns) of pronotum less than 1 1/2 width of head (Fig. 10). Texas and northern Mexico
M. vogti Cartwright
Fig. 9. M. thersites distance between apices of anterior angles (horns) of pronotum nearly twice width of head
Fig. 10. M. vogti distance between apices of anterior angles (horns) of pronotum less than 1 1/2 width of head

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
11 (2').
.		 Pronotum with median, anteriorly directed horn. Mexico (Sonora and Sinaloa)
M. pachecoi Cartwright
 

11'.
.

 Pronotum without median, anteriorly directed horn; anteromedial tubercle or swelling may be present
.
12
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
12 (11).
.		 Cephalic horn at base on dorsal surface with tooth or process (Fig. 11)
 

12'.
.

 Cephalic horn at base on dorsal surface without tooth or process (Fig. 12)
Fig. 11. M. mars cephalic horn at base on dorsal surface with tooth or process
Fig. 12. M. thersites cephalic horn at base on dorsal surface without tooth or process

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
13 (12).
.
.
 Anterior angles of pronotum produced into acute, anteriorly projecting horns (Fig. 13). Color dull or shiny black. Scutellum on disc rugose. Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Panama, Peru, Suriname, Venezuela
 

13'.
.
.

 Anterior angles of pronotum produced into acute, antero-laterally projecting horns (Fig. 14). Color shiny black. Scutellum on disc punctate. Brazil
.
M. mars Reiche
Fig. 13. M. actaeon anterior angles of
pronotum produced into acute, anteriorly projecting horns
Fig. 14. M. mars anterior angles of pronotum produced into acute, antero-laterally projecting horns

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
14 (12).
.
 Pygidium on disc glabrous (some setae basally). Body color black. Southern Arizona
M. punctulatum Cartwright
 

14'.
.

 Pygidium on disc uniformly setose. Body color reddish-brown.
.
15
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
15 (14).
.
 Anterior angles of pronotum (horns) with apices rounded. Pronotum lacking median tubercle. Southern California
 

15'.
.

 Anterior angles of pronotum (horns) with apices spiniform. Pronotum with median, binodose tubercle. Mexico (southern Baja California)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
16 (1').
 Pronotum on disc rugose or rugopunctate.
 

16'.

 Pronotum on disc punctate.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
17 (16).
Elytra with vestiture.
 

17'.

 Elytra without vestiture.

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
18 (17) .
 Scutellum at base rugose.
 

18'.

 Scutellum at base finely punctate.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
19 (18) .
 Pronotum with longitudinal, posteromedian carina (Fig. 15). Mexico (southern Sinaloa: Pacific slopes of Sierra Madre Occidental)
 

19'.

 Pronotum without longitudinal, posteromedian carina (Fig. 16).
Fig. 15. M. nogueirai pronotum with longitudinal, posteromedian carina
Fig. 16. M. elephas pronotum without longitudinal, posteromedian carina
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
20 (19').
.
 Side of elytron, behind humerus velutinous (short, erect setae). Southern Mexico to Venezuela.
M. elephas (Fabricius)
 

20'.
.
.
.

 Side of elytron, behind humerus with short, recumbent setae. Southwestern Mexico (Sierra Madre Occidental)
.
.
M. occidentalis Bolívar y Pieltain, Jiménez-Asúa, and Martínez
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
21 (18') .
 Pronotum with longitudinal, posteromedian carina (Fig.17). Brazil.
.
M. gyas (Herbst)
 

21'.
.

 Pronotum without longitudinal, posteromedian carina (Fig. 18). Brazil.
M. anubis Chevrolat
Fig. 17. M. gyas
pronotum with longitudinal, posteromedian carina
Fig. 18. M. anubis
pronotum without longitudinal, posteromedian carina
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
22 (17') .
.
.
 Frontoclypeal suture with acute tubercle. Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Panama, Peru, Suriname, Venezuela
 

22'.
.

 Frontoclypeal suture with binodose tubercle. Brazil, Colombia, Paraguay, Uraguay
M. mars Reiche
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
23 (16') .
 Elytra with vestiture.
 

23'.

 Elytra with out vestiture.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
24 (23). Anterior margin of clypeus with acute, spiniform teeth.
 

24'.
.

 Anterior margin of clypeus with out acute, spiniform teeth. Argentina and Paraguay
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
25 (24).
.		 Frontoclypeal suture with transverse, blunt tubercle. Tubercle impressed on top. Mexico (southern Baja California)
 

25'.
.

 Frontoclypeal suture with blunt tubercle. Tubercle not impressed on top. Mexico (central Baja California: Cedros Island)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
26 (23').
.		 Frontoclypeal suture with tubercle on distinctly convex, raised surface (Fig. 19). Texas and northeastern Mexico
M. vogti Cartwright
 
26'.
.
.		 Frontoclypeal suture with tubercle on flat surface (Fig. 20). Southern Arizona, Southern California, Mexico (Sonora and Sinaloa).
.
.
27
Fig. 19. M. vogti. Frontoclypeal suture with tubercle on convex, raised surface
Fig. 20. M. pachecoi. Frontoclypeal suture with tubercle on flat surface
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

27 (26').
.
.

Ocular canthus subquadrate with length medially subequal to length distally. Ocular canthus with anterior margin weakly oblique (10 º angle from perpendicular). Southern California
 
27'.
.
.
Ocular canthus subtriangular with length medially 1.5 – 2.0 times larger than length distally. Ocular canthus with anterior margin strongly oblique (45 º angle from perpendicular). Southern Arizona or Mexico

.
.

28
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
28 (27') .
.
.
Elytral punctation near base with sparse, small punctures mixed with moderately dense, moderately large punctures (Fig. 21). Mexico (Sonora and Sinaloa)
.
M. pachecoi Cartwright
 

28'.
.
.

Elytral punctation near base with dense, small punctures mixed with moderately dense, moderately large punctures (Fig. 22). Southern Arizona
.
M. punctulatum Cartwright
Fig. 17. M. pachecoi
elytral punctation
Fig. 22. M. punctulatum
elytral punctation