REPORT ON THE EFFECTS OF COLD UPON THE SCALE INSECTS OF 

 THE ORANGE IN FLORIDA. 



i By Joseph Voyle. 



Gainesville, Fla., December 10, 1883. 



Sir: I have the honor to present the following report of experiments 

 made with cold temperatures on scale insects injurious to orange trees. 

 These experiments were made for the purpose of obtaining some infor- 

 mation as to the extent of relief given by frost to infested trees, there 

 being a very general belief that any damages to the tree by frost are 

 fully compensated for by the destruction of injurious insects. Several 

 successive winters with cold of such severity as to, in some cases, seri- 

 ously damage orange trees, having been followed by heavy swarms of 

 destructive scale insects, gave reason for doubting the truth of the 

 accepted theory. During the past winter, 1882-'83, by some special 

 observations, positive evidence was obtained that often very little dam- 

 age was done to scale insects by cold that killed the tender orange 

 shoots. On the morning of December 16, 1882, the thermometer was 

 reported at various figures, from 19° to 25° F. My own lowest read- 

 ing was 25°. On this morning I cut orange branches incrusted with 

 scale insects and found young migratory larvae of Mytiiaspis running 

 about quite lively. 



By your direction I entered upon a series of experiments that should 

 as nearly as practicable solve the question of "What temperature is fatal 

 to the larvae and to the eggs of these scale insects ? " The laboratory 

 of the East Florida Seminary, with its apparatus, was placed at my 

 service for this work, but fire destroyed the building and contents be- 

 fore the work was begun. It was therefore necessary to devise some 

 inexpensive means of accomplishing the work. The final result of ex- 

 periments for this purpose was a freezer composed of three tin cylinders 

 of 10 inches, 6 inches, and 2 inches diameter, respectively. The 6 inch 

 was placed within the 10-inch, and by means of a collar both were 

 fastened together and the space between them filled with dry feathers; 

 another collar then fitted on, and all soldered tight. A suitable collar 

 being fitted to both ends of the 2-inch cylinder (which was only 10 

 inches in length, the others being 14), it was placed within the 6-inch, 

 equidistant from the ends, and soldered tight, thus leaving room for a 

 head 2 inches thick and 6 inches diameter at each end, the heads being 

 packed with dry feathers. Thus was obtained a central chamber within 

 an empty annular chamber, surrounded by another annular chamber 

 filled with a good non-conductor; the central chamber for the speci- 



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