I am sends you copies textual of the key of Endrody the difference for Dyscinetus and Cyclocephala:
10 (21) Anterior tarsi of males tickened, inner claw usually much bigger than other and strongly curved, apex simple or insiced.
11 (20) Propygidium without long setae
12 (16) apex of clypeus rounded, truncated or emarginated.
13 (19) Clypeus variable, but never short trapezoidal, anterior margin of pronotum never produced in the middle.
14 (15) Clypeus more or less strongly contracted towards the front, apex runded and either truncated or emarginated. Never dilated to apex. Mandibles narrow short. Antennate 8 -10 jointed. Club in males often more or leass longer than in females. Surface yellow with or without black spots, or dark brown to black. 25- 50 mm ....... Cyclocephala Latreille, 1829
!5 (14) Clypeo lightly dilated towards the front apex truncated or lightly rounded. Antenna 10 jointed. Species very similar to those of preceding genus. 9-17 mm. only A. fuliginea Burm. 25- 30 mm.............Aspidolea Bates,1888
16 (12) Apex of clypeus obtusely or sharply acuminated..............Mimeona Casey, 1915, Ancognatha Erichson, 1847
19 (13) Clypeus short trapezoidal sides nearly straight, very strongly contracted toward apex, apical margin lightly rounded,Mandibles broad, out sides without teeth. truncated or lightly emarginated. Antennae 10 jointed. Small club always very short. mandibles broad. Anterior margin of pronotum often produced in the middle, basis not bordered. Anterior tarsi of males slightly thickened. Inner claw often somewhat bigger than other one.Black species. 12- 24 mm.- In tropiouical and temperates zones of America................................... Dyscinetus Harold, 1869
20 (11) Propygidium with long setae. Mandibles broad. Antennas 10 jointed. Club short. basi of pronotum not bordered. Body contracted both forwards and back wards. Anterior tarsi of males strongly thickened. Outher side of elytra in females often distinctly enlarged or tickened. 11- 29 mm.............................Chalepides Casey, 1915
21 (10) Anterior tarsi simple also in males, not tickened.. other genera:....... Stenocrates, Erioscelis, Coscinocephalus, harposceles, Surutu
The real difference of Cyclocepahala and Dyscinetus is in the item 13 (19) but in fact, when when you observe many specimens you can see the difference between both genera.