GARDEN INSECTS 217 



Have the class hunt over the trees, shrubs, and vines 

 in their gardens and bring in specimens of the scale 

 insects that they find. 



The oyster-shell bark louse, Mytilaspis pomorum, is a 

 common and easily distinguished scale, found often on 

 the apple, pear, currant, and sometimes on the plum. The 

 scale covering the female insect is about one-sixth of an 

 inch in length, of characteristic oyster-shell form, some- 

 times completely incrusting the bark (Fig. 92). The males, 

 which are not often seen, are smaller than the females 

 and occur generally upon the leaves. The adult male is 

 a minute two-winged fly whose relationship to its mate 

 or parent could scarcely be suspected. By turning over 

 one of the female scales any time during the fall, winter, 

 or early spring, the eggs may be seen with the aid of 

 a magnifying glass, sometimes as many as a hundred 

 under a single scale. If an infested twig be placed in a 

 bottle of water in the schoolroom, preferably one on each 

 pupil's desk, in late May or early June, the eggs will soon 

 hatch, and the young scales, appearing to the unaided 

 eye as minute, crawling specks, may be seen swarming 

 over the twig. In this stage they are without scaly cov- 

 ering, but after distributing themselves and finding suit- 

 able places, they settle down, insert their piercing beaks, 

 begin to secrete a scale, and the females never again 

 change their locations. Later in the season they are fer- 

 tilized by the winged males, and by August the body of 

 the female insect is little more than a bag of eggs. In 

 the early autumn the eggs are extruded underneath the 

 scale, and the body of the female shrivels to a scarcely 

 recognizable speck at the small end of the scale. Thus, 



