DOSAGE REQITIREMENTS. 41 



all the immature white flies were in the pupal stage. Of the many 

 thousands of specimens examined in the course of the experiments, 

 less than five were in earlier stages. The principal experiments 

 were conducted in the grove at the laboratory in Orlando, Fla., 

 but cooperative experiments were conducted on a larger scale in an 

 extensive grove in the western portion of Orange County. The 

 detailed records concerning the efficiency of fumigation against 

 the white fly refer to experiments conducted at Orlando. A group 

 of trees was selected for treatment on account of the comparative 

 abundance of the live insects. As it was considered desirable to 

 examine the insects both before and after treatment, leaves were 

 selected at various distances from the ground, and in various sections 

 of the tree, and the number of live and apparently normal pupae 

 was noted on a tag which was left attached to each leaf. After 

 fumigation examinations were made at intervals of a few days until 

 the appearance of the pupae on the tagged leaves showed, beyond 

 doubt, that the insects were dead or, if unaffected, until the evidences 

 of normal vitality were unmistakable or the adult insects had emerged. 



The acid used in the experiments, with the exception of experiments 

 Nos. 45.37, 60.21, X.7, andX.8, was tested with a Beaume hydrometer 

 and found to be 66°, as guaranteed by the manufacturers. The 

 potassium cyanid was guaranteed to be 99 per cent pure. A sample 

 was analyzed in the Bureau of Chemistry of the Department of 

 Agriculture and it was reported to contain 40.59 per cent cyanogen, 

 a little more than 0.5 of 1 per- cent more than that theoretically 

 present in chemically pure potassium cyanid, the excess being due 

 to a trace of sodium cyanid. 



As has been previously stated, the sheet tent used was made of the 

 brand of 8-ounce duck which is most used in California for fumigat- 

 ing tents. The tent was untreated but was thoroughly shrunk by 

 exposure to heavy dews and therefore as tight as those ordinarily 

 used. 



A system of numbering the experiments was adopted which 

 indicates the length of exposure and consecutive number of the tree 

 treated for the particular duration of time. The number before the 

 decimal point indicates this exposure for sixty minutes and less. 

 Exposures ranging from one and a half to three hours are indicated by 

 the letter X preceding the decimal point. 



Table IV summarizes the data based upon the experiments of 

 January and February, 1907, concerning dosage for the white fly, 

 including for convenience the dosage called for by the tables found in 

 the appendix. 



