40 
Psyche 
[June 
slower than normal. In the respirometers the animals remained quiet 
in the range —2.5° to 11.3°C. Above this temperature they showed 
increased activity, struggling violently in the vessels. At 18.0°C they 
struggled for the first half hour and then became abnormally quiet, 
but still responsive to tapping. At 20.5°C the two specimens ap- 
peared to be in poor condition, moved feebly, and finally fell to the 
bottom of the vials and curled up after 20 minutes exposure. At 
this point the respirometers were shifted to a 6°C water bath and 
the oxygen consumption followed for an hour, during which time it 
fell continuously. The following day the animals were still para- 
lyzed, showing a low oxygen consumption, feeble heart beat, and in- 
creasingly weak reponses to prodding. The female existed two and 
the male four days in this condition before dying. 
Thermohia. — The oxygen consumption of Thermohia was de- 
termined at various temperatures in the range 1.0° to 51.3°C. The 
results are given in Figure 1. 
The slope of the log QO 2 — temperature curve of Thermohia 
from 12° to 50°C is practically identical with that of Gryllohlatta, 
the average Q 10 being 2.8. The temperature characteristic for this 
range was 15,100 calories (see Fig. 3). Below 12°C the slope in- 
creased to 3.8 and the temperature characteristic became 23,300. 
At 1.0° and 51.3°C the animals were irreversibly injured. Below 
12°C activity was not observable, though the insects would make 
slow, appendicular movements when prodded. On return to room 
temperature, after exposure to the range 3° to 12°C, they became 
normally active within 3 to 20 minutes. Between 12° and 50° C 
activity appeared normal. 
B. Heart activity: 
Gryllohlatta. — Over the range —2.5° to 29.5°C, heart rate in 
beats per minute was recorded and plotted as shown in Figure 2. 
The heart rate — temperature curve approximates a straight line, 
although there is a tendency toward levelling off and decline above 
20° C, which may be due to heat damage. The average Qk), figured 
from —2.0° to 28.0°C is 2.1. Excluding possibilities of damage and 
resulting deviation at temperature extremes, a mass Arrhenius plot 
(Figure 4) gives a slope of 2.8 over a conservative intermediate 
range of 0° to 18°C, with a resulting temperature characteristic of 
12,800 calories. 
At about 2°C the beat became rather feeble, at 0° it was hardly 
discernible, and after a few minutes at — 3°C no form of heart ae- 
