citrus mealybug vs mealy bug

citrus mealybug and mealy bug both are nouns.

Word	Noun	Adjective	Verb	Adverb
citrus mealybug	Yes	No	No	No
mealy bug	Yes	No	No	No

As nouns, mealy bug is a hypernym of citrus mealybug; that is, mealy bug is a word with a broader meaning than citrus mealybug:

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

Other hypernyms of citrus mealybug include mealybug.

citrus mealybug (noun)	mealy bug (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