10 
take effect by direct action on the grubs, laboratory 
experiments are comparatively useless without field 
trials accompanying them, because it is rarely that the 
strength of solution needed to kill the grub can be 
brought to bear upon it practically without killing the 
plant it infests. Also, though the fluid may be strong 
enough to kill the larva if it touched it on the surface, 
yet its effect is rapidly weakened by passing through 
the earth; and further, the grub has in most cases both 
the instinct and the power to remove itself gradually 
from the annoyance, if any is caused to it by the 
chemical application filtered down into the ground. 
We had some good information bearing on these 
points in the joint observations made in 1880, agri¬ 
culturally by Mr. Fitton on his farm near Nantwich, 
in Cheshire, chemically by Mr. Smeatham, of Liver¬ 
pool. In this case the grubs of the Daddy-long-legs 
were the kind experimented on, and it was found that 
in a solution of four per cent, of carbolic acid in water 
they were killed in from one to two minutes. In a 
solution of one part of the acid to 250 parts of water 
they were killed in eight minutes. The effect of the 
strong solution was tried in the field, and it proved 
useless—on examination the grubs were to be found 
within an inch of the ground which had been watered 
with the mixture. Sulphate of iron and sulphate of 
copper killed the grubs (in laboratory experiment) in 
about ten minutes, or rather less; lime appeared to 
have no effect upon them. In experiments made by 
Mr. George Brown, of Watten Mains, Caithness, as to 
effect of salt on the same kind of grubs, it was found 
that they went down lower and lower in the ground 
according to the strength of dressing- applied. 
I have no notes of the effect of direct application of 
chemicals to wireworm, but the observations regarding 
experiment on Tipulce larvae (that is to say Daddy- 
long-legs grubs) will serve to illustrate the point gener¬ 
ally to which I desire to draw your attention. If we 
know, have it proved, that some common chemical 
likely to be tried has no effect ac all on any given crop 
pest, this knowledge is valuable so far as it goes, for it 
saves the loss of time and capital in trying what its 
effect may be when the enemy is in the fields. But we 
greatly need to understand clearly and correctly in 
what way many dressings and applications which are 
known to be serviceable as preventives in cases of 
attack act on the grubs or insects. Most grubs appear 
rather to die of starvation than to feed on what is not 
suitable ; if we can manage to fairly imbue the soil 
with anything which in solution must necessarily be in 
some degree swallowed by the grub as it feeds on the 
roots in the dressed ground, we must benefit (also in 
some degree) by the application. We find that in some 
cases the grub sinks deeper and deeper in the ground to 
avoid the unwholesome presence, just as it does in the 
case of increasing frost, but as yet, as far as I am aware, 
we have no field experiment on these points. Every 
year the same loss of time and of material goes on in 
trying, as it is said, and whilst the trial is going forward 
