is orange to reddish orange. The male cover is similar to that of the female but is 
smaller, more slender, and has a submarginal shed skin. 
The walnut scale has one generation per year and overwinters as second instar 
males and females in Maryland (//68); overwintering second instars molt and 
mature from mid to late April. Eggs and first instars are present from late June to 
late September. Second instars begin to appear in early September. This scale may 
kill entire trees in some situations, although infested trees usually have dead lower 
branches and few leaves, giving them a weakened appearance (605). Natural 
enemies include at least six species of parasitic wasps, two lady beetles, and a green 
lacewing. 
The European fruit scale, Q. ostreaeformis (Curtis), is apparently native to 
Europe and is present in 11 Northeastern States from Maine to Pennsylvania west to 
Ohio. Hosts include a variety of plants, but rosaceous trees, especially apple, most 
commonly act as hosts. This species is found in natural and ornamental vegetation. 
The cover of the adult female is circular, convex, dark gray, and has orange or 
yellow subcentral shed skins. The male cover is similar to that of the female but is 
smaller, more slender, and has a yellow subterminal shed skin. 
The European fruit scale has one generation per year in Germany (/066), 
Czechoslovakia (722), and New Zealand (/024). In Europe the species overwinters 
as second instar males and females, but in New Zealand it overwinters as first or 
second instars. Adults are present in spring or early summer. Eggs and crawlers 
appear in late June or July. Males are essential in at least some populations. The 
European fruit scale may damage fruit trees in some parts of Europe and the United 
States. Natural enemies include at least five chalcidoid wasps, several lady beetles, 
and a fungus. 
The San Jose scale, Q. perniciosus (Comstock), is Oriental in origin and occurs 
throughout the United States (fig. 38). It is polyphagous but is commonly collected 
on pyracantha, pears, Prunus spp., and many other rosaceous hosts. The species 1s 
found in natural and ornamental vegetation. The cover of the adult female is 
circular, slightly convex, gray, and has yellowish subcentral shed skins. The body 
of the adult female is yellow. The male cover is similar to the female cover but is 
smaller, elongate oval, and has yellow subterminal exuviae. 
- Courtesy Conn. Agric. Exp. Stn. 
Figure 38.—San Jose scale, 
Quadraspidiotus perniciosus. Note 
large number of immature scales. 
120 
