84 [ DISEASES OF CITRUS TREES 



dish brown colour perfectly smooth and smaller than that 

 of the preceding. Its margin is surrounded by a rim of 

 waxy filaments. The young insect is yellow and slightly 

 oval. This scale is rarely found on Citrus trees, and is 

 much more frequent on certain ornamental trees, such as 

 Schinus Molle, and on ferns growing in the open air. 



Lecanium Ci/ri may be only a variety of L 

 hesperidum. 



The Lecanidae like other scale insects are partheno- 

 genetic. The Black Scale is rarely found on the leaves 

 or on the fruit, but is very common on the twigs and 

 branches. The Hemispherical Scale is never found on 

 the leaves exposed to the full action of the sun. In 

 autumn the impregnated females of Lecanium die leaving 

 their scale filled with a mass of eggs numbering from 

 400 to 600. These are hatched in spring, and the young 

 larvae soon quit their mother scale in quest of a 

 new abode. 



The genus Ceroplastes, so called on account of the 

 thick waxy scales which cover the insect, numbers three 

 species, which have been noticed on the orange tree. 



Ceropiastes floridemis Comstock, is about 3mm. 

 in length, oval-shaped, having a rounded prominence in 

 the centre surrounded by six or eight smaller ones. 

 These prominences are white and the depressions 

 between them have a pinkish tinge due to the colour of 

 the insect under the scale. The eggs, about 100 in 

 number, hatch under the shelter of the scale, and the 

 young larvae escaping from beneath the scale disperse 

 in all directions When they begin to secrete their waxy 

 covering they move only by night, and as they advance 

 in age most of them assemble on the twigs and branches. 



Ceroplastes cirripediformis Comstock, the Barnacle 

 scale, is a little larger than the preceding. Its covering 

 consists of one central convex plate surrounded by six 

 lateral ones, each plate having its proper nucleus ; the 



