THE EUROPEAN ELM SCALE IN THE WEST. 11 



ACTIVITIES OF THE FEMALE. 



The hibernating female larva? begin their activities a little later 

 than the male larvae. In fact, most of them show no signs of 

 activity until March, when they begin molting for the last time 

 (PL IV, B). The white cast skins appear quite conspicuous on the 

 bark. The newly molted or virgin females are smooth and of a 

 dull brown or greenish-brown color. After mating they move 

 about and settle down for the last time, most of them selecting the 

 lower side of the larger limbs and branches. They soon take on a 

 grayer appearance and begin to form waxy fringes of cotton or 

 semicocoons about the margins of their bodies. By the middle of 

 May they have about completed their semicocoons and are full 

 grown, ready to begin oviposition. Egg laying lasts for several 

 months, or until about the middle of August. During this time 

 the females have slowly shriveled and die upon completing ovi- 

 position. 



Soon after molting to the third stage the females begin excret- 

 ing honeydew, and do not stop until egg laying is completed. This 

 drops onto the foliage and the ground beneath, making the trees 

 and ground very sticky. A black smut fungus grows in this sticky 

 material, giving the foliage a black appearance which can be seen 

 for gr:at distances. 



SEASONAL HISTORY. 



There is only one generation a year of the European elm scale. 

 The second-stage male and female larvae are the forms hibernating. 

 Late in January in the milder climates a few 'of the male larvae 

 start forming cocoons in which to pupate. These become more 

 abundant during February and March. Adult males begin emerging 

 from their cocoons in February, becoming more abundant in March 

 and April. A few of the last to transform emerge in May. 



The hibernating female larvae molt for the last time in March 

 and April, whereupon they move to a proper place for the summer 

 and mate. They soon begin to increase considerably in size, at 

 the same time forming waxy semicocoons about their bodies. Egg 

 laying starts the last of May or the first of June and continues 

 through June, July, and part of August. Having completed ovi- 

 position the females shrivel and die. 



The eggs hatch in less than an hour after being deposited and the 

 tiny yellow larvae crawl about, some settling on the twigs and 

 branches, but most of them settling along the midribs of the leaves. 

 About the middle of July the first of these larvae molt for the first 

 time, becoming reddish brown and later gray from the sugary 

 particles of wax which are* secreted over the back. The last of the 

 yellow larvce molt early in September. These second-stage brown 

 or gray larvae are the overwintering forms, and are found mostly 

 clustered about the winter buds and in the rough areas of the twigs 

 and branches. 



A definite relationship has been observed between the activity of 

 the European elm scale and its host. As the events in the life cycle 



