STUDIES ON, PERILLUS BIOCULATUS FAB. 7i 
at a temperature near 4°C. ‘The first bug selected was undercooled 
to an internal temperature of —9.2°C., when a rebound occurred to 
—2.08°C., thereby indicating the actual freezing point. The second 
specimen undercooled was reduced to —g.74°C. when the rebound 
occurred and indicated —2.24°C. as the freezing point. Four more 
individuals were frozen but not one could withstand undercooling to 
a point lower than —9.18°C. It might be added that all these specimens 
were undercooled carefully to prevent shaking, which night cause in- 
oculation prematurely, thus to determine so far as possible the limit 
of undercooling in an undisturbed insect. All bugs that were actually 
frozen, that is, in which a rebound in temperature took place, indicating 
crystallization, were killed even tho removed immediately from the 
freezing chamber. 
Table 3 summarizes the data obtained from freezing ten specimens 
of Perillus, the first six on April 15 and the last four on April 17. 
TABLE 3 
Rebound to: 
Freeze Undercooled to: (freezing point) 
Bug No. (trial) Gs ns 
I Ist —Q.20 =P. 
2nd —7.20 —2.01 
2 Ist —0:74 —2.24 
3 Ist —8.17 —1.79 
4 Ist —g.18 —2.08 
5 Ist ——f90) —1.70 
2nd —7.70 —1.79 
6 Ist —8.13 ste 
2nd = 5\(62 —i.61 
7 Ist —7.60 —1.52 
2nd —7.60 —1.56 
ard —6.79 —1.48 
4th —8.13 —1.50 
8 Ist —8.40 =e 
2nd —7.86 =i.0s 
3rd == 5 (0) See! 
S Ist OS ae on 
2nd —09.03 —2.13 
3rd —8.50 —1I.90 
4th —7.40 —1.90 
5th se —1.90 
6th —3.70 ——1.70 
10 Ist —7.16 —1.74 
and aad —1.88 
