ladybug vs lady beetle

ladybug and lady beetle both are nouns.

Word	Noun	Adjective	Verb	Adverb
ladybug	Yes	No	No	No
lady beetle	Yes	No	No	No

As nouns, ladybug and lady beetle are synonyms defined as:

ladybug and lady beetle: small round bright-colored and spotted beetle that usually feeds on aphids and other insect pests

Other synonyms of ladybug include ladybeetle, ladybird, ladybird beetle.

ladybug (noun)	lady beetle (noun)
small round bright-colored and spotted beetle that usually feeds on aphids and other insect pests	small round bright-colored and spotted beetle that usually feeds on aphids and other insect pests