For P.
waltl and P. cultripes in particular, explosive events in
which thousands of individuals emerged and moved
towards their breeding sites during autumn or winter
days were common in Don˜ana 30–40 years ago
(Valverde, 1967; Dı´az-Paniagua pers. obs.); however,
they have not been observed since 1990 (Dı´az-
Paniagua et al., 2005).