EFFECT OF COLD ON SCALE EGGS. ee) 
J think there is hardly any limit to the application of a water-proof 
insecticide when applied with a proper apparatus.—[ WILLIAM PLUMER, 
Lexington, Mass., January 22, 1883. 
[We were very glad indeed to receive the full account of Mr. 
Plumer’s experiments with water-proof insecticides. For a number of 
years past we have been at work at the same point, especially with refer- 
ence to the Southern cotton-worm, and the latest and most satisfactory 
results in preventing the washing off of insecticides by rain have been 
obtained by the perfecting of machinery for spraying the under-sides of 
the leaves. <A long series of experiments with adhesives, such as dex- 
trine, mucilage, gum-arabic, and molasses show that such substances 
can be used to some considerable advantage, but that this advantage 
is soon. limited by the closing of the stomata of the leaves, thus injur- 
ing the plant, and by the interference which they offer to the use of a 
very fine spray. With Mr. Plumer’s particular formula we have not 
experimented, but we will see that careful trial of it is made next season. 
His experiments, as given in his letter of the 22d instant, are interest- 
ing, but we are rather skeptical as to the use of pennyroyal for the cur- 
culio, as we have always found that this insect was very slightly affected 
by malodorants, and it is so easy to mistake a natural disappearance 
for the result of a remedy. | 
DESTRUCTION OF SCALE INSECTS BY GOLD. 
* * * YT mail you with this a piece of orange branch covered with 
Mytilaspis that has been submitted to a temperature lower than usually, 
if ever, occurs in this State. It was first placed in the chamber of the 
glacier at atmospheric temperature 82° F., and the temperature gradu- 
ally lowered to 42° during one hour; then the cooling was forced, and 
left for four hours, when the reading was 24°. The indices were then 
brought to contact, the chamber closed, the cooling forced, and then left 
for twelve hours. At the end of that time the chamber was opened, and 
the maximum immediately read, being 30°. The minimum index read 
16°. Therefore, after cooling for five hours, the coccids were subjected 
for twelve hours to a temperature commencing with 24° F., descending 
to 16°, and not rising above 30°. A microscopic examination was im- 
mediately made. No sign of life was found in the larvie examined. The 
eggs appeared natural. After drying in the atmosphere the forms of 
many of the larve appeared shrunken; some eggs had collapsed, leav- 
ing white forms; others retain, after twenty-four hours, their usual 
form. They will be examined from day to day, to see if any of them 
can bear the treatment, and hatch, so as to be a guide for the next 
freezing. * * * —{Jos. VOYLE, Gainesville, Fla., May 15, 1883. 
|A careful examination of the scales received failed to show any live 
eggs. | 
