CHAPTER XLI. 

 INSECTS INJURIOUS TO CITRUS TREES. 



The insects attacking citrus trees may be conven- 

 iently grouped as biting and sucking insects. The first 

 group, including the grasshoppers, orange-dog and a few 

 other insects of less importance, injure the trees by eat- 

 ing the foliage and other tender parts. The sucking 

 insects, however, obtain their food from the trees by 

 sucking the juices out of the cells. Many of them also 

 appear to inject a poisonous substance into the tissues 

 which assists in destroying the cells. The members of 

 this second group are far more numerous than those of 

 the first; in fact, the most dreaded insect enemies of 

 citrus trees are found here. This group may be further 

 divided into Scale Insects and Insects other than Scales, 

 the latter embracing the white fly and different kinds of 

 mites. The scales may be divided into armored or pro- 

 tected scales and unarmored or unprotected scales. The 

 armored scales have a protective covering and are unable 

 to move about after having once settled themselves in 

 a certain position. The unarmored scales have no hard 

 covering and are motile during the greater part of their 

 existence, moving freely while young, but in a very lim- 

 ited way when matured. If we present a graphic out- 

 line of the groups of the more important citrus insects 

 as described in this chapter we have 



I. Biting Insects. 



II. Sucking Insects. 



(1). Scales, (a) Armored Scales, (b). Un- 

 armored Scales. 



(2). Insects other than Scales, (c) White Fly. 

 (d) Citrus Mites. 



