katydid \ka"tydid`\, n. zool.
   a large, green, arboreal, orthopterous insect cyrtophyllus
   concavus of the family locustidae, 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
see also:
cyrtophyllus concavus locustidae