208 FIELD AND HEDGEROW. . 
will grow, but not beyond, just as if you had run a sepa- 
rating ditch round the mountain. With the flora the in- 
sects cease ; whether the germ comes from the vegeta- 
tion or from the insect that frequents the vegetation 
does not seem known. Still it would be worth while to 
make a careful examination of the plant and insect life 
just at the verge of the line of division. The bacillus 
may spring from a spore starting from a plant or start- 
ing from an insect. Most of England had an Alpine 
climate probably once, and some Alpine plants and 
animals have been stranded on the tops of our highest 
hills and remain there to this day. In those icy times 
English lungs were probably free of disease. Has formic 
acid ever been used for experiments on bacilli? It is 
the ant acid ; they are full of it, and it is extracted and 
used for some purposes abroad. Perhaps its strong 
odour is repellent to parasites. To return: while the 
honey-bees live in comparative safcty, the more or less 
solitary wild bees have a great struggle to repel various 
creatures that would eat them or their young, and, be as 
watchful as they may, all their efforts at nest-building 
are often rendered nugatory by the success of a parasite. 
So it is not worth while to catch them just for the pur- 
pose of identification, for they have enough enemies in 
the field without man and his heartless cabinets. The 
collector is the most terrible parasite of all. Let them 
go on with a happy hum, while the tulip opens in the 
sunshine. 
