EFFECT OF COLD ON SCALE EG<;S. <•> 



I think then* 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 otter 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 remedv.l 



Destruction of Scale Insects by Cold. 



* * * I 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 

 tor 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 live hours, the coccids were subjected 

 for twelve hours to a temperature commencing with 24° F., descending 

 t<> 16°, and not rising above 30°. A microscopic examination was im- 

 mediately made. No sign of life was found in the larva- examined. The 

 eggs appeared natural. After drying in the atmosphere the forms of 

 many of the larva 4 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, ami hatch, so as to be a guide for the next 

 freezing. * * * — [Jos. Voyle, Gainesville. Fin.. May 1~>. L883. 



[A careful examination of the scales received tailed to show any live 

 eggs.] 



