INJURING THE BRANCHES. 



149 



filthy and unsightly, as well as impairing their 

 vitality by extracting the sap. A single one of the 

 aphides hatched from the egg in spring may become 

 the' ancestor of many millions before autumn. But 

 in October a true sexed generation develops, the 

 males being winged and the females wingless. By 

 the union of these two the true eggs are obtained. 

 The wingless forms, whether viviparous or ovipa- 

 rous, do not differ materially in appearance. The 

 oviparous, or egg-laying, form is' represented at Fig. 

 74 : it is about one-fifth of an inch long, bluish- 

 black in color, with a glaucous bloom. It has a 

 distinct white longitudinal line along the middle of 



Fig. 76. Spotted Aphis: a, egg, magnified ; b, oviparous females 

 depositing eggs. 



the back, and a row of white spots along each side. 

 The cornicles, or honey -tubes, are bright orange yel- 

 low. The male (Fig. 75) is one-fifth of an inch long, 

 with a wing expanse of one-third of an inch. The 



