LATINOS love telling the tale of "La Llorona". La Llorona's purpose is very akin to that of El Cuco. Meant to warn children to stay out of trouble and not wander in the dark. If they don't the cuco is supposed to eat you, whereas La llorona will kidnap the children and never return them. La Llorona story is said to have come from Mexico, but no one really knows where it originated from. There are many different versions of La Llorona.
The most common one is about a peasant girl named Maria, who had a beauty like no other. Maria had many suitors. She however, didn't pay attention to any of the men of her village, but she did fall in love with a wealthy man who was mutually interested in her. They united and had children. He later decided Maria wasn't the one for him and ended the relationship to be with another woman (so unlikely of a Latino man). He wanted to be with someone of his social and financial status. Out of spite, Maria, went to the riverbanks and drowned her children. Quickly after realizing what she had done she tried saving them, but it was too late. Her agony led her to commit suicide.
When Maria tried to enter the heavens, a saint told her she needed the soul of a child with her to be granted entrance. Resulting in Maria's spirit roaming the earth in search of her children or other kids to snatch and take with her as she cries, "Mis niños, mis niños, donde estan mis niños?!" (My children! My children! Where are my children?!). Like we mentioned earlier, the tale is told differently and varies by country, but more or less it is a similar plot and setting. People claim that if they pass by the riverbanks during nighttime they can't see her, but they could hear her crying.
This is why Latino children behave SO well, because they don't want La llorona to take their little arse.