1950] Edwards and Nutting — Thermobia and Grylloblatta 43 
strongly suggests physiological adaptation and perhaps even tax- 
onomic subspeciation. 
Summary 
The oxygen consumption, heart rate, and activity at various tem- 
peratures over the range —5.0° to 51.3°C have been determined for 
the firebrat, Thermobia domestic a Packard and for Grylloblatta 
campodeif ormis Walker. 
Grylloblatta is normally active from —2.5° to 11.3°C. At lower 
temperatures activity is decreased and at higher temperatures ac- 
tivity is increased until at 18.0° the animals become stuporous and 
at 20.5 °C become irreversibly damaged by heat. Over the range of 
temperatures from —2.5° to 20.5°C the log Qio — temperature 
curve is a straight line, having the slope of 2.7 per 10 degrees. In 
this range the temperature characteristic for oxygen consumption 
is 14,600 calories. In the range —2.5° to 29.5°C the curve relating 
heart rate to temperature resembles the respiratory curve giving an 
average Qio of 2.1. In the intermediate range of 0° to 18°C an 
Arrhenius plot of heart rate gives a slope of 2.8 and temperature 
characteristic of 12,800 calories. 
Thermobia is active throughout the range 12° to 50°C. Below 12° 
it becomes inactive, and is irreversibly injured by cold at 1°C. At 
50° activity decreases and heat injury becomes apparent at 51.3°C. 
The log QO 2 — temperature curve has a slope of 3.8 per 10° from 
3° to 12°C, and a slope of 2.8 between 12° and 50°C. Temperature 
characteristics for respiration in these ranges are 23,300 and 15,100 
calories respectively. The heart rate — temperature curve is prac- 
tically identical with the respiration curve, giving an average Qio 
of 2.6. The temperature characteristic for heart beat in the inter- 
mediate range of 15° to 45°C is 12,300 calories. 
These two insects extend the general insect metabolism — tempera- 
ture curve, and appear to be strictly poikilothermal in that they 
make no metabolic adaptation to offset unfavorable temperatures. 
Literature Cited 
Adams, J. 
1933. Biological notes upon the fire-brat, Thermobia domestica (Pack- 
ard) . Jour. New York Ent. Soc., 41: 557-562. 
Campbell, M. G. 
1948. Notes on Grylloblatta at Kamloops. Proc. Ent. Soc. British 
Columbia, 45: 1-5. 
