The Bulletin. 11 



Hibernation. — When really cold winter weather comes on the insects 

 cease to breed. During the winter the adult insects nearly all die, so that 

 it is mostly the partly grown insects that pass the winter. However, in 

 warm winters we have known the insects to breed even in midwinter on 

 warm days in the warmer sections of the State. 



How Does the Scale Spread? — We have seen that the insect can only 

 crawl about for a few hours after birth, and that therefore it could only 

 spread very slowly, and only during the breeding season, if it were 

 entirely dependent upon its own powers. As a matter of fact, however, 

 there are various outside agencies which aid them in spreading into new 

 trees, new orchards and new localities. Chief among these outside agen- 

 cies are: (1) Wind, (2) Birds, (3) Insects, (4) Commerce in nursery 

 stock. These, with its own limited natural powers, constitute its princi- 

 pal methods of spread. We will consider each of these separately, con- 

 sidering first its natural powers. 



Natural Spread. — If one of the young insects should start out as soon 

 as born and run as rapidly as it could until it became necessary for it to 

 settle down and begin to feed, it could only travel a short distance, per- 

 haps one or two rods. It is evident, therefore, that the vast majority of 

 the young insects settle on the same tree on which they are born. If the 

 trees are so set and pruned that the branches of separate trees do not 

 interlock, it will be almost impossible for the young insects to get from 

 one tree to another of their own accord, and this is an important point, 

 for the spread of the scale in thickly set orchards may be very materially 

 lessened by keeping the branches so pruned that they shall not reach from 

 one tree to another. But in spite of this the insects will usually spread 

 to the other trees more or less rapidly by other means. 



Spread hy Wind. — Notice that we have said that the young insects are 

 very, very small ; therefore, if a wind blows through the orchard during 

 the breeding season (from April to December) the young crawling insects 

 are liable to be blown about from place to place like particles of dust. 

 Indeed, in almost every case where a large orchard becomes infested it 

 is to be noted that it spreads most rapidly in the direction of the prevail- 

 ing winds. Of course it is mere chance whether the young insects which 

 are thus blown from one tree will find lodgment on another, and these 

 winds no doubt leave many thousands to die on the ground. But it is 

 perfectly evident that many are spread from tree to tree by this means. 



Spread by Birds. — If a bird alights in a scale-infested tree at any time 

 during the breeding season some of the young insects may crawl upon its 

 feet or feathers and be carried off into other trees, there to crawl off 

 again. There can be no doubt that they are often established on new 

 trees in this way. We have frequently found in our inspections that the 

 portion of a tree close around an old bird's nest may be thickly infested, 

 while other parts may be slightly infested or almost entirely free from 

 the insect. In towns and villages we have found similar evidence, the 



