530 HEMIPTERA. 



face of the body, and is identical with the flocculent matter, or 

 down, that exudes from certain Aphides and the shell lac insect 

 and related forms. On the other hand, Dr. Shimer, who has 

 given the fullest history of this insect, and was the first to 

 make observations for the most part similar to those recorded 

 above, considers that the scale consists of the several (three) 

 cast skins of the larva, "cemented by some kind of an exuda- 

 tion to the bark." This insect can be best exterminated by 

 scraping the bark, and then washing the trees with soapsuds a 

 few days after the trees blossom, just as the young are about 

 hatching. Dr. Shimer has discovered a mite 

 (Acarus? malus Shimer) which sucks the 

 eggs in autumn. 



Another species, which is native, the As- 

 pidiotus Harrisii of Walsh (Figs. 533, 534, 

 A, B, showing the two kinds of scales) dif- 

 fers in the scale being oval, "almost entirely 

 flat, and of a pure milk white color," with 

 red eggs, while those of the Oyster shell 

 bark-louse are milk white, and the larvae 

 are at first blood red. It occurs on the apple 

 and pear, and is far less injurious than the 

 other species. 



Fig. 533. PSYLLID^E Latreille. These small Leaf- 



hoppers are found hopping over the surface of leaves and often 

 raising galls. They are flattened and provided with short legs 

 and a broad head, and covered with a white cottony mass in 

 the larva state. In the mature insect the forked antennae are 

 eight to ten-jointed, with two slender terminal bristles forming 

 the fork. There are three remote ocelli; the beak is three- 

 jointed, reaching to the 

 middle of the chest, and 

 the epimera of the meta- 

 thorax terminate behind in 

 an acute spine on each 

 side. The limbs are short, 



with thickened shanks, and two-jointed tarsi. The wings are 

 thickened and folded roof-like over the body, and the three 



