400 INSECTS INJURIOUS TO THE ORANGE. 



No. 255. The Ribbed Scale. 



Icerya purckasi Maskell. 



The adult female of this species of Coccus is covered by 

 an egg-sac, which is of a pale-yellowish color, longitudinally 

 ribbed, a little longer than the body of the insect, and filled 

 with a loose, white, cottony matter containing the eggs. A 

 cluster of these sacs is shown in Fig. 410, of the natural size; 



the enclosed insect is of a 

 dark orange-red color, with 

 black antenna? and legs, its 

 back being covered more or 

 less with a white or yellow- 

 ish-white powder. 



The eggs are said to num- 

 ber from two hundred to five 

 hundred in each cluster, and 

 are of a pale-red color. The 

 newly-hatched larva is red- 

 dish or brownish, with long 

 and slender legs. As it grows 

 it gradually changes, becom- 

 ing darker in color and irreg- 

 ular in outline, and it soon begins to excrete tufts of waxy 

 matter along the back and sides, following which long, semi- 

 transparent filaments appear. 



These insects first attack the leaves, usually along the 

 midrib, and afterwards migrate to the twigs and branches, 

 and sometimes attach themselves to the trunk. They spread 

 with amazing rapidity on orange and lime trees, the trunks 

 and limbs of which are sometimes so completely covered 

 with them as to appear white ; the leaves turn yellow and 

 sickly, and if no remedial measures are adopted the trees 

 sometimes die. The insect has been found very destructive 

 at Santa Barbara, where it has probably been introduced with 

 plants from Australia. 



