Natural Spread of Insects. 25 
other country. A comparatively harmless insect in 
France becomes the dreaded horn-fly in America. 
Again, the demand for legislation usually arises be- 
cause of the incursion of some new intruder, but a 
pest is commonly worst when newly introduced, 
for, like a prairie fire, it finds its course unimpeded. 
After a time it reaches an approximate limit to its 
furious spread, parasites overtake it, and other pests 
contest its feedmg grounds. Nearly all insect pests 
lose much of their terrors after they have once 
run over the country. This is admirably illustrated 
in the potato-bug.* In other words, the first ap- 
pearance of a pest in formidable numbers is apt to 
result in a seare, to which, it is to be hoped, the San 
José scale, which is now attracting so much atten- 
tion in the east, is no exception. The fact is, 
that insect and fungous pests are inevitable, and 
the farmer can have no peace of mind until he 
accepts the fact, and then resolutely prepares to 
meet them, both by strategy and direct battle. Yet, 
if now and then a serious pest can be kept out of 
the country, even for a few years, by means of in- 
spection upon the frontiers, the effort may be emi- 
nently worth the while. 
*Tt may as well be said, once for all, that the writer uses the word bug 
for any hard-shelled insect. The entomologist uses it technically for a 
certain classificatory group of insects, and he generally insists that every- 
one else use it in the same way; but it should be remembered that the 
word was a common-language term long before the entomologist impressed 
it into special use. This common usage, therefore, has prior rights; and 
since it is impossible to make people use it in the entomological sense, it 
is plain that the entomologist must be prepared to accept any confusion 
which arises from his use of it. He can probably arrive at his purpose quicker 
and better by using purely technical terms. 
