80 [ DISEASES OF CITRUS TREES 



of Algeria and Northern Italy. It appears that the 

 original host of this scale insect was the jujube-tree, 

 Zizyphus saliva Gaertn., although in this Island jujube- 

 trees growing in the midst of infested orange-trees enjoy 

 perfect immunity. Perhaps the Parlatoria finding that 

 Citrus trees being evergreen are a more desirable host 

 for its requirements, has forsaken its original host and 

 adapted itself to the new host, a not infrequent event in 

 the life history of insects. This scale insect appeared for 

 the first time in Malta in 1892, in certain orange groves 

 at Casal Lia, having been imported from Palermo along 

 with a collection of ornamental varieties of Citrus trees. 

 Its dissemination was overlooked for the first three years, 

 but soon after the infection began to spread rapidly, and 

 orange merchants refused to purchase the unsightly fruit. 

 Parlatoria Lucasi is a small oval-shaped scale insect 

 of a black colour, surrounded by a narrow rim of white 

 wax, which also covers the surface of the scale and 

 gives it a dark blue shade. Its length is about i. m.m., 

 and at one end it has a small round or oval scale which 

 is the first larval skin. The male insect is smaller ; it is 

 covered only by the first black shield and by a white 

 elongated scale of wax, the large black scale being 

 absent. After the second moult the larva of the male 

 passes to the pupa stage, and finally becomes a winged 

 insect, lacerates the waxy covering, and goes out to 

 winged life. 



Parlatoria Lucasi has certainly four broods during 

 the year. The first appears early in spring, perhaps 

 earlier than that of other scale insects. The young are 

 seen in April already covered with their larval skin on 

 the new shoots and sometimes even on the blossoms 

 before blooming. The tiny pale -coloured larvae hardly 

 discernible without the aid of a lens, may be seen 

 crawling upon the leaves, especially along the nerves 

 where a slight depression is forming. After a few hours 

 of a wandering life the larva chooses a place where to 



