31 



that it is scarcely noticeable on the surface of the leaf or twig. It is 

 very commonly found on various greenhouse plants, and has been 

 carried to all parts of the world on such material. In climates suitable 

 for the growth of the orange and lemon it occasionally gains a foot- 

 hold on outdoor plants. It has a gregarious habit, and commonly 

 lives in colonies, frequently covering the young limbs and the midribs 

 of the leaves. These colonies are usually not of long duration, being 

 soon attacked and exterminated by parasitic and predaceous enemies, 

 the soft texture of the insect not furnishing much, if any, protection. 

 The transformation and habits are very similar to those of the black 

 scale. It, however, is much more rapid in growth, and, where the 

 climate is favorable, goes through a continuous series of generations, 

 or broods, throughout the season. It readily yields to oily washes or 

 to the gas treatment. 



The Hemisplierical Scale. 



This scale {Lecanium hemisphaericum Targ.— fig. 24) is also distinc- 

 tively a greenhouse pest, and it can 

 hardly be considered as especially 

 injurious to citrus trees in orchards. 

 It occurs all over the world, and occa- 

 sionally will multiply to a slight extent 

 on orchard trees. The individuals are 

 about the same size as those of the last 

 two species. In color it ranges from 

 light brown in the young to dark brown, 

 changing to reddish in the old scale. 

 The adult scale is hemispherical in 

 shape perfectly smooth and shiny, and 

 this, with its color, readily distinguishes 

 it from the other two species. The remedies are those used against 

 the black scale. 



The Florida Wax Scale. 



This very curious and striking scale insect {Ceroplastes floridends 

 Comstock) secretes a white waxy covering, arranged in a very regular 

 geometrical pattern (fig. 25). It was long known from Florida, where 

 it is undoubtedly native, its principal food plant being the gall berry. 

 It has nowbeen carried, however, to other parts of the world, notably 

 some of the adjacent West Indian islands, and also to the Old World. 

 It was imported into California on stock from Florida in 1889, and 

 possibly earlier, but has never gained any foothold on the Pacific 

 coast. This insect often occurs on citrus plants, though rarely in 

 sufficient numbers to be of very great importance. The white color 

 and striking appearance of these scales cause them often to be noted, 



172 



Fig. 2-1.— Hemispherical scale {Lecanium 

 hemisphxrimm) : a, characteristic group 

 of adult scales on olive— natural size; 

 b, three female scales— considerably eu;^ 

 larged; c, scale lifted from leaf, showing 

 mass of eggs (original) . 



