658 C. B. HARDENBERC4. 



These birds flying away will carry the young bagworms with 

 them, and when the bird comes to rest on another tree they 

 can crawl off and establish themselves there. In a block 

 which has already been loaded with bagworms as a result o£ 

 wind infestation, the arrival of these few extra individuals 

 will not make any difference, but where this has occurred in 

 a plantation or block free from bagworms the results are 

 rather striking, in that we find in the entire block only a tree 

 or two infested at the tip. This may be distinguished as a 

 true bird infestation, cases of which are by no means rare 

 and account for the presence of bagworms in small numbers 

 in plantations which, through an exceptionally favourable posi- 

 tion, escape the gross infestation by wind or air currents. 

 Inappreciable at first, such occurrences may give rise to an 

 accumulative infestation in succeeding years (see later). 



Another agent which could cause a similar type of infesta- 

 tion might be furnished by insects flying through the webbing 

 made by the young bagworms, and carrying some larvas along 

 with them. Fuller suggests cockchafer beetles as the most 

 likely to be the carriers in this case. Of course, it would 

 have to be a fairly robust type of flying insect, as the smaller 

 ones would become hopelessly entangled in the mass of web- 

 bing. But, unfortunately for the hypothesis, the cockchafer 

 beetles have not yet made their appearance during the hatching 

 period of the bagworms, their time of emergence being about 

 a month to six weeks after the hatching of bagworms and 

 their distribution is passed. As a matter of fact, the writer 

 has examined several flying insects for the presence of young 

 bagworms attached to them, but has not been able to find 

 any evidence to suppoi't this theory. While not precluding 

 the possibility of such an occurrence, the probabilities are so- 

 slight as to make this possible factor negligible. 



(c) Mammals. — We meet sometimes with another type of 

 infestation, which excludes the possibility of its having been 

 caused by the wind or by a bird, and which only can have 

 been caused by some other individual carrier. This is the 

 type which I have called a sporadic infestation, \vher& 



