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THE BROWN ANT IN ORANGE ORCHARDS. 



By O. W. Barrett, Entomologist and Botanist, 

 Porto Rico Agricultural Experimental Station. 



Excepting the scale insects the most serious pest at present af- 

 fecting young orange trees in Porto Rico is the Brown, or Stinging 

 Ant, Solenopsis geminata, Fab. It lias already caused very serious 

 damage to citrus stock in many localities and unless immediate 

 measures are taken to check its increase, greater loss will follow. 



Ordinarily this species of ant lives in rather small colonies of 

 about 5,000 to 15,000 individuals in nests in the soil and subsists 

 on small seeds, dead insects, and the honey-wax secreted by scale 

 parasites. Upon becoming established in an orange orchard, how- 

 ever, this ant forms at the foot of the tree a nest composed of se- 

 veral galleries, or passages, extending to a depth of about 6 inches 

 and having I to 3 openings at the surface of the soil close to the 

 trunk. A nest may contain a dozen or more queens if it is well 

 established, and these qeeens deposit the numerious eggs near the 

 ends of the burrows, where the young ants may be found in all 

 stages of growth. From this nest the working individuals, ac- 

 companied by the "soldiers," or large-jawed ants of the colony, 

 pass up the tree trunk to feed upon the wax-like substance secreted 

 by the scales and to obtain the gummy excretion from the wounds 

 which they make in the bark of the twigs and branches for this 

 purpose. They also frequently damage the flowers, young fruit, 

 and terminal buds : even small twigs are sometimes completely 

 severed by their gnawing through the tender wood in their greedi- 

 ness to obtain a rapid flow of the gum. 



A colony of these ants may live at the base of a tree for several 

 weeks, merely feeding upon the wax of the scales and doing no 

 injury to the bark, but when they have once acquired a taste for 

 the gum they seem to prefer it to the wax. The worst feature of 

 this acquired habit is the formation of open sores at the base of 

 the trunk ; the continual biting of the margins by the ants gradu- 

 ally enlarges the wounds and, if not attended to, these sores spread 

 and commingle till the tree is girdled. 



In view of the fact that grave financial loss has already resulted 

 in many of the citrus orchards of this Island through loss of trees 

 from the attacks of this ant and through the injurious effects of 

 various chemical mixtures applied experimentally to the trees in 

 combating the pest, it seems advisable to urge the use of the fol- 

 lowing safe, cheap, and simple remedies which we have found to 

 be the most practicable of a dozen or more similar mixtures. 



GIRLE PAINT. 



Unless covered with some substance which keeps out the air 

 and water, the exposed wood in the wounds of the trunk is a me- 

 nace to the life of the tree, not only through loss of sap by evapo- 

 ration but by rotting of the wood and poisoning of the sap resul- 

 ing from water entering the cracks. 



