### Instruction:
What are 3 differences between the arabica and robusta species of coffee?

### Input:
Of the two main species grown, arabica coffee (from C. arabica) is generally more highly regarded than robusta coffee (from C. canephora). Robusta coffee tends to be bitter and has less flavor but a better body than arabica. For these reasons, about three-quarters of coffee cultivated worldwide is C. arabica. Robusta strains also contain about 40–50% more caffeine than arabica. Consequently, this species is used as an inexpensive substitute for arabica in many commercial coffee blends. Good quality robusta beans are used in traditional Italian espresso blends to provide a full-bodied taste and a better foam head (known as crema).

### Response:
First, robusta is considered to be more bitter and less flavorful than arabica. Second, robusta contains 40-50% more caffeine that arabica. Third, because of the higher bitterness and less flavorful quality of robusta, about 75% of all coffee cultivated in the world is arabica making it much more popular than robusta.