katydid

from WordNet (r) 3.0 (2006)

katydid
    n 1: large green long-horned grasshopper of North America; males
         produce shrill sounds by rubbing together special organs on
         the forewings

from The Collaborative International Dictionary of English v.0.48

Katydid \Ka"ty*did`\, n. (Zool.)
   A large, green, arboreal, orthopterous insect ({Cyrtophyllus
   concavus}) of the family {Locustid[ae]}, common in the United
   States. The males have stridulating organs at the bases of
   the front wings. During the summer and autumn, in the
   evening, the males make a peculiar, loud, shrill sound,
   resembling the combination Katy-did, whence the name.
   [1913 Webster]