_Oyster-shell scale._--This is an elongate scale or bark-louse, 1/8 in.

in length, resembling an oyster shell in shape and often incrusting the bark of apple twigs. It hibernates as minute white eggs under the old scales. The eggs hatch during the latter part of May or in June, the date depending on the season. After they hatch, the young may be seen as tiny whitish lice crawling about on the bark. When these young appear, spray with kerosene emulsion, diluted with 6 parts of water, or whale-oil or any good soap, 1 lb. in 4 or 5 gal. of water.