TASK DEFINITION: You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For simplicity, answers should be in all lower cased letters.
PROBLEM: Category: INSECTS 
Clue: This snout beetle reached Texas from Mexico around 1890 & spread into most cotton-growing areas of the U.S.

SOLUTION: the boll weevil

PROBLEM: Category: ROYALTY 
Clue: Mswati III became the king of this country in 1986 when he was 18

SOLUTION: swaziland

PROBLEM: Category: ROMAN EMPERORS 
Clue: To eliminate opposition, Septimius Severus replaced these imperial bodyguards with his own troops

SOLUTION:
praetorian guards