SEASONAL-VARIATION IN FREEZING TOLERANCE OF THE NEW-ZEALAND ALPINE COCKROACH CELATOBLATTA-QUINQUEMACULATA

1. The cold hardiness of the alpine cockroach Celatoblatta quinquemacu lata was investigated. This species is found at 1360 m a.s.l. beneath schist slabs on the Rock and Pillar Range (Central Otago, New Zealand) . Cockroaches were collected monthly from January to December 1996, an d their LT50 and supercooling points determined. 2. Celatoblatta quinq uemaculata was freezing tolerant throughout the year, with a lower let hal temperature in winter of -8.9 degrees C. Celatoblatta quinquemacul ata was also found frozen under rocks in the field when the under-rock temperature was below 3 degrees C, and could survive being frozen at -5 degrees C for 3 days in the laboratory. 3. There was a marked decre ase in LT50 temperature from -5.5 degrees C in April to -7.5 degrees C in May. This coincides with decreasing temperatures from summer throu gh autumn to winter, during which temperatures beneath snow-covered ro cks may reach -7.3 degrees C. 4. Supercooling points fluctuated during the year, with an increase from -4.2 degrees C in autumn to -3.4 degr ees C in winter. Supercooling point was highest in spring, and changes in supercooling point do not appear to be related to changes in LT50 5. Recordings of environmental temperatures from the Rock and Pillar R ange suggest that cockroaches may undergo up to twenty-three freeze-th aw cycles in the coldest month of the year, and that they may remain f rozen for periods of up to 21 h. Maximum cooling rates recorded in the field (0.01 degrees C min(-1)) were 100-fold slower than laboratory c ooling rates, so survival estimates from laboratory experiments may be underestimates.