Cold hardiness of Pyrrhocoris apterus (Heteroptera : Pyrrhocoridae) from central and southern Europe

The cold hardiness of individuals from overwintering populations of a freez e susceptible bug Pyrrhocoris apterus from central and southern Europe diff ered significantly. Supercooling point (SCP) correlated well with both leth al temperature (LT50) and lethal time (Lt(50)), and is a good index of cold hardiness of adults during and after diapause. In January, diapause termin ated, but cord hardiness was similar to that recorded in November; cold har diness decreased slightly in March and markedly in May. Short exposure (les s than a week) to higher temperatures before termination of diapause did no t reduce the cold hardiness. Cold hardiness did not closely follow air temp eratures. The Bulgarian bugs retained lower cold hardiness regardless of ac climation to harsh field conditions in the Czech Republic. The interpopulat ion difference is therefore a heritable character representing an adjustmen t to local climates.