Walker (1962) studied the mating songs of male tree crickets. Each
wingstroke by a cricket produces a pulse of song, and females may
use the number of pulses per second to identify males of the
correct species. Walker (1962) wanted to know whether the chirps
of the crickets Oecanthus exclamationis (abbreviated exis) and
Oecanthus niveus (abbreviated nius) had different pulse rates. See
https://www.biostathandbook.com/ for details. (The
abbreviations are made from the the first two and last two letters
of the species.) He measured the pulse rate of the crickets
(variable pps) at a variety of temperatures (temp):