THE ARGENTINE ANT IN RELATION TO CITRUS GROVES. 33 



In San Diego County, therefore, the conditions are such that the 

 mealybug infestation is just as persistent in trees where there are no 

 unts as in other localities overrun by them. This infestation may 

 remain severe for from one to several seasons, and then there will 

 come a period when the mealybugs will disappear almost wholly. 

 This fact has just been illustrated in the Chula Vista district, and 

 is no doubt due to variations in abundance of the mealybug enemies 

 in that section. 



INFLUENCE OF THE ANT ON ABUNDANCE OF OTHER MEALYBUGS IN CALIFORNIA. 



The number and severity of outbreaks of other species of mealy- 

 bugs in Pasadena have been increasing during the last three years. 

 Dr. A. G. Smith, county horticultural inspector for the Pasadena 

 District, states that in an inspection five years ago, covering the dis- 

 trict bounded by Fairoaks, Colorado, and Lake Streets and the Alta- 

 dena boundary line, only one mealybug infestation was found. An 

 inspection three years ago of the same section of Pasadena produced 

 18 infestations, mostly on rice-paper plants. During the summer of 

 1916, up to the time this information was given, only the north half 

 of this section, or from the Altadena line to North Orange Grove 

 Avenue, had been inspected, but infestations were found in numerous 

 places and on many more host plants than ever before. The worst 

 of these outbreaks have occurred in territory invaded by the Argen«- 

 tine ant, and undoubtedly have been especially severe and persistent 

 only where attended by this ant. 



A number of the outbreaks discovered by Dr. Smith's inspectors 

 early in the summer of 1916 had been greatly reduced, and the mealy- 

 bugs had almost disappeared by August where there were no ants in 

 attendance. The species concerned in these outbreaks and the host 

 plants most commonly infested in this section are as follows : Pseudo- 

 coccus citrophilus Claus. on pittosporum, oignonia, tecoma, citrus; 

 Pseudococcus bakeri Essig. on Chamaerops and Washington palms, 

 peppers, laurestinas, nightshade, tomato, banana, aralia, fig, cam- 

 phor, and various garden plants; Pseudococcus longispinus Targ. 

 on Dracaena palms, citrus, and some shrubs ; Pseudococcus ryard Coq. 

 on cypress hedge. Outbreaks of these species of variable degree 

 occur every spring, but are less persistent and usually are controlled 

 earl} 7 by their natural enemies where no ants are present. 



Another species, known as the golden mealybug {Pseudococcus 

 ourilanatus Mask.), attacks the Araucaria tree in many localities 

 about Pasadena and remains numerous throughout the summer, 

 regardless of whether ants are present or not, and often causes the 

 defoliation of the trees. This mealybug either is not controlled by 



