The Pear Tree Pstlla. 233 



Although the indications of the presence of some enemy is 

 thus so conspicious, the depredator is an insect so small as to be 

 easily overlooked. 



The Appearance of the Insect. 



The immature insect. Figs. 1 and 2. — These curious minute, 

 oval, immature forms are called nymphs. When first hatched 

 they are of a translucent yellow color, and hardly visible to the 

 unaided eye; eighty of them placed end to end would scarcely 

 measure an inch. They increase in size quite rapidly and undergo 

 gradual changes in color and form until they measure .055 of an 

 inch in length and .045 of an inch in diameter; the natural size 

 is indicated by the hair line at the right of the figures. These 



W 



Figure 2. — Full grown nymph, ventral view; a, anus; b, beak. 



fuU grown nymphs are oval in ehape, and of a general blackish 

 color often tinged with red; the eyes are of a bright crimson 

 color. A very conspicious feature is the large black wing pads 

 on each side of the body. The whole body is very much flattened, 

 being only one-fifth as thick as long. 



The adult insect. Fig 3. — From the full-grown nymph, the 

 change is to the adult insect. In this foim th*.^ pest strikingly 

 resembles a Cicada or Dog-day -Harvest-fly in minature. It would 

 take nine or ten of them placed end to end and about forty placed 

 side by side to measure an inch; the hair line beside the figure 

 indicates the natural size of an adult. From the wide blunt 

 head, the body tapers considerably to the sexual organs at the 



30 



