Source : Webster's Revised Unabridged Dictionary (1913)

Ladybug \La"dy*bug`\, n. (Zo["o]l.)
   Same as {Ladybird}.

Source : WordNet®

ladybug
     n : small round bright-colored and spotted beetle that usually
         feeds on aphids and other insect pests [syn: {ladybeetle},
          {lady beetle}, {ladybird}, {ladybird beetle}]