72 BULLETIN NO. 4, DIVISION OF ENTOMOLOGY. 
reported, 19° F., be correct, scale insects with only moderate protection 
should have been killed, and all their eggs with them; but such was 
not the case. Both thermometers and readings are often questionable. 
Unreliability of graduation of common instruments, particularly below 
the temperate figures, and readings made by parties unaccustomed to 
accuracy, may be taken as a reasonable explanation of wide discrepan- 
cies. 
There are conditions practically unattainable artificially, where the 
coecids are protected from the effects of such temperature as under 
favorable conditions would be fatal to them. The leaves of the tree, 
the warm current rising from the ground around the trunk of the tree, 
and the initial heat of the tree itself perform an important part in mod- 
ifying temperature for these insects. Inastill atmosphere this might be- 
come a perfect protection against a temperature much lower than would 
prove fatal in other conditions. Again, acold, moist breeze following a 
rain might lower this protection to a fatal point. Casual observation 
warrants the supposition that these conditions do occur with the results 
as supposed. Valuable information could be obtained by using regis- 
tering thermometers within the protection of the head of the tree, and, 
on the outer branches; a comparison of records would indicate the 
amount of protection, and give data for ascertaining approximately the 
amount of cold required to reduce the temperature all over a tree to a 
point absolutely fatal to coccids: probably a temperature fatal to the 
tree also. 
The table has been arranged from the notes so as to present results 
without unnecessary details. The experiments were repeated for veri- 
fication, and also whenever any results were doubtful. 
The table may be regarded as an aceurate exponent of the effect of 
low temperature on orange coccids. 
Table showing results obtained by exposing orange scale insects to various degrees of cold. 
| | [ee | 
| | | Time from 
i “ies | 
| Minimum | exposure | 
. Maximum | >; Avan lt yas 1) apiece 
ae en tempera- | tempera- | pees Reeul te | hate | to final Remarks. 
p ; ture. ture. |) POSE: Pia A ie So |) resulta, | 
| egos 
| | | PSss. 
} | Hours. | | Days. 
Lee sere 16 24 | 5 Dead ...| Dead - 31 
Opreee ssa | 19 32 | 10 SHO) soe doeese- 12 
Bicaosenose | 20 25 10 eer cere cs doi 25.] 4 
URE eee | 22 22 5 -do dO 7 
Dinsae ceases | 22 22 3 do doimese- 12 
Gz | 22 22 il SOO) Aes () saeec 14 
i oe POE 23 23 1 (iki See lIee doe 2431 14 
(Fea oper oes | 25 34 10 200. seer ee do 20 
Qe cwesies | 25 25 | 5 mi PRR eel sisae 12 
1 ese ans ae | 25 34 16 On eka | Hatch -- 8 3 eggs only out of a 
large number. 
