SCALE INSECTS OF IMPORTANCE 297 



Appletree bark louse 



Mytilaspis pomorum Bouche 



PLATE I 



This is the most common scale insect found on fruit trees in New York, 

 and in some localities it is very abundant and destructive, particularly to 

 poplars and ash 'in the vicinity of Albany. This pest has been repeatedly 

 noticed in agricultural and entomologic journals, and it is a frequent 

 source of complaint at the present time. A few of the more important 

 articles treating of this insect are given in the brief bibhography below. 

 This European species was probably brought to America on early impor- 

 tations of fruit trees, and now it is known to occur all over the world, as 

 stated by Dr L. O. Howard. It has been described scientifically several 

 times, on each occasion receiving a different name, and it also passes 

 under the common name of oyster shell bark louse. The popular desig- 

 nation given above is extensively used, and it is preferable on account of 

 its being more characteristic of the species. 



Description. The adult female scales can easily be recognized by a 

 comparison with the greatly enlarged figure 7 or with figure 9, which lat- 

 ter represents a number in natural size on poplar bark. The adult scale is 

 about 3 mm, or \ inch long, usually slightly curved and widening from 

 a slender tip to a broad, rounded posterior end. The scale has at its 

 pointed or anterior end a usually yellowish, very small pellicle, the first 

 cast skin of the young, and a small scale three times its size attached to 

 it. There is also a larger or second cast skin, and to it is attached the 

 larger or chief part of the scale, which is a variable brown and marked 

 with curved transverse lines or wrinkles. The first cast skin can be 

 detected only on microscopic examination. The female insect found 

 underneath the covering scale is represented in figure lo. The male 

 scale is smaller, and is shown in figure 6. A female scale turned over in 

 winter presents the appearance represented in figure 8. The shriveled, 

 yellowish- or brown body of the female occupies the anterior portion of 

 the scale cavity, while in the posterior part are numerous oval, white 

 eggs, shown greatly enlarged in figure i. The minute, yellow, recendy 

 hatched scale insect is represented in figure 2, and the condition of a 

 number shortly after establishing themselves on a twig, in figure 3. The 

 appearance of the young after it has secreted a protecting scale is repre- 

 sented in figure 4, a few being shown much enlarged in figure 5. 



Lite history. This insect completes the round of life once a year in 

 this latitude, though in the southern states two generations may be pro- 



