Planococcus citri vs mealybug

Planococcus citri and mealybug both are nouns.

Word	Noun	Adjective	Verb	Adverb
Planococcus citri	Yes	No	No	No
mealybug	Yes	No	No	No

As nouns, mealybug is a hypernym of Planococcus citri; that is, mealybug is a word with a broader meaning than Planococcus citri:

Planococcus citri: feeds on a wide variety of cultivated plants but especially destructive to citrus
mealybug: scalelike plant-eating insect coated with a powdery waxy secretion; destructive especially of fruit trees

Other hypernyms of Planococcus citri include mealy bug.

Planococcus citri (noun)	mealybug (noun)
feeds on a wide variety of cultivated plants but especially destructive to citrus	scalelike plant-eating insect coated with a powdery waxy secretion; destructive especially of fruit trees