314 CITRUS FRUITS 



give them a cloudy appearance, while a few others have 

 markings on their wings which produce a slight variation 

 and give a different appearance. 



The life histories of all of the whiteflies are very similar. 

 These insects have complete metamorphoses, that is, they 

 pass through four stages in their development. 



The egg is small and nearly oval in outline. It is barely 

 visible to the naked eye. The eggs are laid on the under side 

 of the leaves of the plant and hatch in a few days into pale 

 yellow larvae. The larvae crawl about for a few hours, usually 

 on the underside of the leaves, and soon insert their beaks 

 into the tissue, where they suck out the sap. They never 

 move again, but continue to feed and grow rapidly, going 

 through several molts until they reach the fourth larval 

 stage, which differs from the larva of the other stages in 

 being thicker, taking less food, and the organs of the adult 

 fly begin to form. The insect passes through this last stage 

 and emerges as an adult fly. The life as an adult is very 

 short, in most cases only a few days. The females lay about 

 a hundred eggs and then die. 



The whitefly can be held in check by spraying. Spraying 

 with a combination of soap and oils will serve to control 

 these insects. The original spray recommended by the 

 Florida Agricultural Experiment Station is as follows : 



Whale oil soap 8 pounds 



Paraffin oil 2 gallons 



Water 1 gallon 



More recent experiments have demonstrated that by 

 substituting other soaps which are cheaper, just as good 

 results are obtained. The modified formula then is to sub- 

 stitute two pounds of ordinary soap for the whale oil soap 

 and then heat the material to the boiling-point and emulsify 

 it by agitating it vigorously. This stock solution should 

 be diluted before it is used. 



The number of sprayings that are necessary to control the 

 whiteflies depends upon the weather and the location. The 

 first spray should be given late in April or early in May. 

 The best time seems to be when the bulk of the spring brood 



