40 EEPOET OF SEARCH FOE ENEMIES OF CITRUS WHITE FLY. 



down the natural enemies cf this pest as well. Probably the adults of 

 Prospaltella never emerge from the majority of parasitized larvae and 

 pupse of the fly, and this because of theu- destruction by heat previous 

 to the time for theii" exit. This same extreme weather which limits 

 the white fly to two distinct broods has both a direct and an indi- 

 rect eft'ect on the lady-beetle. Since this insect destroys only the 

 younger stages of the white fly, the heat has an indirect effect by 

 limiting the breeding of the pest to two distinct broods, so that there 

 is only a very short time in the spring and in the fall during which 

 food for the coccinellid is available. The direct effect is that the ex- 

 treme heat produces a deterrent influence on the lady-beetle's activity. 



It may be well to state what could be expected of these natural 

 enemies if established in Florida. At the very maximum of possible 

 efficiency the writer believes they would fall far short of commer- 

 cially controllmg the white fl}^. In fact, it is very doubtful if its - 

 commercial control by natural enemies alone is possible. Granting 

 that this high degree of control could not be expected, the writer's 

 observations and experience lead him to believe that the introduction 

 of these natural enemies, especially the lady-beetle, is likely to result 

 in sufficiently beneficial results to be well worth the while. Espe- 

 cially would this be so when these natural <enemies were working in * 

 connection with the different fungous enemies of the fly now found 

 in Florida. 



The elimination m this country of the checks to the development 

 of these natural enemies, which exist in India, would assuredly have a 

 beneficial eftect. Whereas in India the white fly can be found on 

 citrus trees only in small quantities and is limited to two distinct 

 broods, the situation is entirely changed in Florida in that there are 

 several broods in a single year. The presence of an adequate food 

 supply throughout a large part of the year, in a climate in which the 

 most extreme day of summer is sufficiently mild to allow thek free 

 acti\dty, would seem to present such a favorable situation that these 

 natural enemies of the white fly must needs accomplish excellent 

 results after becoming thoroughly established. 



DESIRABILITY OF CONTINXJIN'G THE ATTEMPT TO INTRODUCE 

 THESE TWO NATURAL ENEMIES. 



It has been pointed out m the preceding discussion that conditions 

 in Florida appear favorable to splendid results from the establish- 

 ment of these natural enemies, especially the lady-beetle {Cryp- 

 tognaiha Jlavescens) . As previous experience has shown how best to 

 cope with the situation in order to carry it tlu'ough to a successful 

 termmation, the present would seem an inopportune time to termi- 

 nate endeavors in parasite introduction. We have detailed informa- 

 tion of localities in which to find the natural enemies, the proper 



