MySQL foreign keys on self

I'm currently trying to make a self referencing table in MySQL, however it seems I can't make a foreign key on the table itself, I'm getting an MySQL error:

Error Code: 1005. Can't create table 'biological classification' (errno: 150)

This is my code:

# Table creation
DROP TABLE IF EXISTS `biological classification`;
CREATE TABLE `biological classification` (
  `idBC` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `idParent` int(11) DEFAULT NULL,
  `type` varchar(45) DEFAULT NULL,
  `value` varchar(45) DEFAULT NULL,
  PRIMARY KEY (`idBC`),
  UNIQUE KEY `idnew_table_UNIQUE` (`idBC`),
  CONSTRAINT `SelfKey` FOREIGN KEY (`idParent`) REFERENCES `biological classification` (`idBC`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB AUTO_INCREMENT=20 DEFAULT CHARSET=latin1 COMMENT='A table that contains the Biological Classification of anima';

# insert into table
INSERT INTO `biological classification` (`idBC`,`idParent`,`type`,`value`) VALUES (1,NULL,'Class','Mammalia');
INSERT INTO `biological classification` (`idBC`,`idParent`,`type`,`value`) VALUES (2,1,'Genus','Giraffa');
INSERT INTO `biological classification` (`idBC`,`idParent`,`type`,`value`) VALUES (3,2,'Species','Giraffa camelopardalis');
INSERT INTO `biological classification` (`idBC`,`idParent`,`type`,`value`) VALUES (5,1,'Genus','Panthera');
INSERT INTO `biological classification` (`idBC`,`idParent`,`type`,`value`) VALUES (6,1,'Genus','Loxodonta');
INSERT INTO `biological classification` (`idBC`,`idParent`,`type`,`value`) VALUES (7,5,'Species','Panthera leo');
INSERT INTO `biological classification` (`idBC`,`idParent`,`type`,`value`) VALUES (8,5,'Species','Panthera tigris');
INSERT INTO `biological classification` (`idBC`,`idParent`,`type`,`value`) VALUES (9,6,'Species','Loxodonta africana');
INSERT INTO `biological classification` (`idBC`,`idParent`,`type`,`value`) VALUES (10,1,'Class','Marsupialia');
INSERT INTO `biological classification` (`idBC`,`idP