San Jose scale
Species (Aspidiotus perniciosus) of scale insect first discovered in North America at San Jose, Cal., in 1880 but probably a native of China. A waxy gray secretion (the scale) covers the yellow females, which are about 0.06 in. (1.5 mm) in diameter. The scale is elevated in the center and is surrounded by a yellow ring. The female produces several generations of living young each year. San Jose scales can completely cover tree branches and may eventually kill the tree.
This entry comes from Encyclopædia Britannica Concise.
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