The Collaborative International Dictionary of English v.0.48:

Melolonthidae \Melolonthidae\ prop. n.
   A natural subfamily of beetles, considered a separate family
   in some classification systems.

   Syn: subfamily Melolonthidae.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Melolonthidae
    n 1: considered a separate family in some classification systems
         [syn: Melolonthidae, subfamily Melolonthidae]