66 [ DISEASES OF CITRUS TREES 



cingulatus, Say. The first is a borer of the roots, and 

 the other amputates twigs about 2 c.m. in thickness by 

 making a circular notch around them after having laid 

 its eggs close to the buds above the notch. He describes 

 and figures also Elaphidion inerme, Newman, whose 

 grub bores into the dead wood. Brachys ovata, 

 Artipus floridanus and other beetles prey upon the 

 leaves but only to a very limited extent. None of these 

 beetles has as yet found its way to our groves. 



On the other hand we have several species of small 

 beetles (Coccinellidae or Ladybirds) which prey upon the 

 scale-insects and other parasites, and help to keep them in 

 check. Their beneficial action will be referred to later on. 



Among the Hymenoptera, the ants are the only 

 insects injurious to Citrus trees in these Islands. They 

 gnaw the tender leaves into an elaborate lace -work, and 

 gnaw asunder the growing ends of young twigs. The 

 injury caused to young trees, and especially to newly 

 budded stock is often considerable. Ants sometimes 

 attack the blossoms and devour the tender ovary. A 

 colony of ants may form its nest into the trunk of a 

 Citrus tree, and by means of the formic acid which they 

 secrete may cause the death of the tree. These colonies 

 may be destroyed by pouring some petroleum upon 

 them, and stopping the door-way with a piece of cloth 

 dipped in the same liquid. Ants may prove troublesome 

 in another direction. When a colony of Toxoptera appears 

 on a twig, the ants are sure to disseminate it all over the 

 tree, carrying the young aphid in their mandibles from 

 one twig to another. They also help to disseminate the 

 scale-insects in the same manner, for the sake of the 

 honey dew which is secreted by the aphid and by the 

 scale-insects. Spraying the trees with a diluted insecticide, 

 such as lysol, etc., or with a diluted solution of 

 sulphate of iron (green vitriol) helps to keep away 

 the ants. Wool or cotton tied round the stem entangles 

 the ants which attempt to pass and acts often as an 



