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MISC. PUBLICATION 62 6, U. S. DEPT. OF' AGRICULTURE 



colonies or clusters (fig. 17) on the new 

 growth, at the base of buds, or on the 

 under sides of the leaves. Infested 

 plants are often visited by large num- 

 bers of ants and other insects that feed 

 upon the honeydew excreted by the 

 aphids. Honeydew is a sweet, sticky, 

 liquid excretion which often coats the 

 leaves or objects below the aphids, 

 giving them a sticky or varnished 

 appearance, or a sooty appearance as a 

 result of a sooty mold developing on 

 the honevdew. 



* 



Figure 17. — Colony of aphids clustered 

 on an ivy stem. About V/i times 

 natural size. 



Aphids are soft-bodied, whitish or 

 greenish to blackish insects with pear- 

 shaped or nearly globular bodies, and 

 they have three pairs of comparatively 

 long legs (fig. 18). They are usually 

 not over % inch in length, and many 

 species are smaller. Most of them are 



without protective covering, although 

 the bodies of some of the woolly aphids 

 are covered with white waxy threads. 

 The rate of development and multipli- 

 cation is rapid, and many generations 

 may be produced in a season. Both 

 winged and wingless forms are produced; 

 the winged forms migrate to start new 

 colonies either on the same type of 

 plant, or, with some species, on an 

 entirely different, or secondary, host 

 plant. Several successive generations 

 may consist almost entirely of wingless 

 females, but when they become crowded 

 or the time for migration comes, winged 

 forms are produced. The young are 

 either hatched from eggs or born alive. 



Figure 18. — Stages of the melon aphid 

 (Aphis gossy-pii Glov.) : a, Winged 

 adult; b, wingless adult. About 10 

 times natural size. 



Certain species of aphids attack the 

 roots of asters (p. 21) and various other 

 plants, whereas other species attack the 

 bulbs of tulip, iris, crocus, and other 

 flowering bulbs (p. 87). 



Treatment. — On the first evidence 

 of aphids or their injury, spray or dust 

 the infested plants with nicotine sulfate, 

 derris, or pyrethrum. Strong soapsuds, 

 made of fish-oil soap or other soaps dis- 

 solved in water, is also an effective 

 spray. Be sure that the insecticide 

 covers the insects. Several applica- 

 tions about a week apart may be re- 

 quired. Do not delay treatment; 

 otherwise the plants may be seriously 

 damaged. Syringing infested plants 

 with water under considerable pressure, 

 and directing the stream to the under 

 sides of the leaves from several angles 

 to dislodge the insects that are congre- 

 gated there, is useful in the case of 

 shrubs and hardier plants, but is too 

 severe a treatment for tender annuals 

 or perennials. 



LEAFHOPPERS 



Leafhoppers are small sucking insects 

 which may injure plants in various ways. 

 The draining of the plant juices may 

 cause a whitening and curling of the 

 leaves and killing of the tender tips, as 



