APPENDIX. 356 



OYSTER-SI TELL SCALE, 



{Mydlaxpis pomoritm, Bouche.) 



15y Pkok. .\i,kxaxi)1-:k Ckaw. 



This scale is very damaging to apple trees, and also infests other plants. 

 The scale of the female is mussel shape, more or less curved, of a purplish- 

 brown color, with the exuviae yellowish. Length, one-sixteenth of an inch. 

 The body of the female is light yellow. The last segment presents the fol- 

 lowing characteristics: The anterior group of spinnerets consists of from 

 eleven to seventeen ; the anterior laterals and posterior laterals each of six- 

 teen to twenty-one. The median lobes are large and wide, with the sides 

 parallel ; they are only about three-fourths as long as broad. Each lobe is 

 narrowed on each side near the distal extremity by one or two notches, and 

 then rounded. The second lobe of each side is about as wide as the first, 

 and is deeply incised ; mesal lobule with mesal margin as long as lateral 

 margin of the first lobe, and rounded posteriorly ; lateral lobule about half 

 the length and width of mesal lobule, and similar in shape. Third lobule 

 obsolete. The plates are long, simple, and tapering. 



Eggs— These are white, and are arranged irregularly under the scale. 



Scale of male — The scale of the male of this species is usually straight 

 and of the same color as that of the female. At about one quarter of the 

 length of the scale from the posterior extremity the scale is thin, forming 

 a hinge which allows the posterior part of it to be lifted by the male as he 

 emerges. Length, six hundredths of an inch. The male is translucent, 

 corneous gray, with a dorsal transverse band on each joint, and the portions 

 of the mesothorax and metathorax darker, or purple gray, with the mem- 

 bers somewhat lighter. 



According to climate and locality the young scale hatch from the middle 

 of March to June. Color, yellow. They begin to form the cottony excre- 

 tion after twenty-four hours, and in two to four days the insect is completely 

 covered with a dense excretion, which increases as the larva grows. 



In several of the older apple-growing districts of the state this scale has 

 secured a lodgment, and in neglected orchards that have been subdivided into 

 city lots they have made considerable progress. 



