Early-warning system

Male katydid, aka bush cricket.

''{W}e know that once he (a katydid) has started to sing, the day is not far off when we shall hear the last hardy individual of his species, barely able to shake off the numbing effects of cold, dragging out a few last chirps. His first song is, for us if not for him, less the beginning of something than a warning that a season is getting near its end.''

--Joseph Wood Krutch, in "The Twelve Seasons''