8 FARMERS’ BULLETIN 650. 
mologist or inspector that the stock is free from the seale. In addi- 
tion to the actual inspection of nurseries, further safeguard is fur- 
nished by the practice of most nurserymen (compulsory in some 
States) of fumigating the plants, before distribution, with hydro- 
cyanic-acid gas. 
After the insect once becomes established in a locality its spread is 
accomplished by various agencies. As explained under the natural 
history of the insect, it is capable of movement only during a short 
period after birth. During this crawling stage the imsects are able 
to pass from tree to tree where the limbs are in contact, but it is 
Fig. 7.—Appearance ofapples infested with the San Jose scale. ( Original.) 
by agencies independent of itself that it is principally distributed. 
Prominent among these factors are birds, which may alight upon 
infested trees, where the young insects may crawl upon their feet 
and be subsequently deposited in other trees, sometimes at distances 
quite remote. It is probable that the young are blown by strong 
winds from tree to tree; and they are carried by insects, such as 
grasshoppers, ladybird beetles, ants, etc. The crawling ‘“‘lice” may 
be transported considerable distances on the clothing of man, on 
vehicles, or on horses or other live stock which may be in orchards 
for any purpose. 
