66 
Supplement to the ''Tfopical Agncultunst.” 
[July I, 1890. 
food which was derived from the soil was how- 
ever liable to exhaustion, and hence the only 
manures a plant would need for its healthy growth 
were of a mineral nature. Liebig was so con\ in- 
ced of this that he went the length of preparing 
a standard manure which came to be most exten- 
sively sold for a time ; but alas, further know- 
ledge not only exposed the falsity of the Mineral 
Theory, but also blasted the xirospects of a thriv- 
ing trade. It was Liebig, however, who in spite 
of his mistakes brought home to Agriculturists 
the need they had for the lielp that science could 
give, and how Chemistry would l)e able to helx> 
them a great deal ; and the year 1840 will always 
be remembered by Agriculturists as an important 
one, for in this year Liebig’s great work was xnib- 
lished. “ If a person were asked,” says Dr. Lawes, 
“ what events had produced the greatest influence 
on Agriculture in Great Britain during the last 
lialf century, he would, undoubtedly, say the 
establishment of the Eoyal Agricultural Society of 
England, and the publication of Baron Liebig’s 
work upon Agricultural Chemistry.” 
It is idle to theorize unless theory can stand the 
test of experiment, and it was only after Bous- 
singaiilt started his experiments in France on his 
own farm, followed by Sir John Lawes atRotham- 
stead in Hertfordshire, that the facts of Agricul- 
tural Chemistry began to be established. Nothing 
could have reached the perfection of experimen- 
tation but energy and x^erseverance such as Dr. 
Lawes possessed. He is essentially an experimen- 
talist, and every statement he puts forward is the 
result of close observation and has stood the 
crucial test of careful exx^eriment under his own 
eye in his outdoor laboratory at Rothamstead. 
Hence it is that we would rather listen to what 
he has to say, innocent as he is of any distinctions 
or honours gained by a laborious University course 
than those of any other man. It is only last 
month that he furnished us Avith an epitome of 
the results of his experiments AX’hich have been 
given in detail by Dr. Feam, the Botanist to the 
Royal Agricultural Society, ■ in the A'olume he 
published not many years ago on the Rothamstead 
experiments. This exntome as gh'ing information 
as to how crops feed is xvorthy the perusal and 
study of every Agriculturist. With regard to the 
much vexed question as to the inability of crops 
to groAv continually, yet in a healthy condition, on 
the same land xvithout artificial aids, we now 
know that this depends on the peculiar feeding 
habits of different families of plants in Aurtue of 
which one kind of plant affects certain ingredients 
of xAlant-food and takes these uxi in larger propor- 
tions to others ; the extent to which roots pene- 
trate into the ground and the cax^ability they have 
for availing them.selves of food in the soil. Hoav- 
ever fertile a soil, the resources of plant food as 
tar as a j^articular croxA is concerned are bound to 
be taxed to an undue extent Avhere that crop is 
groAvn on the same land Avithout the inter A'ention 
of a crox> of a different sxAOcies or Avithout artificial 
aids — esjjecially in the case of agricultural croxis 
that have their xn-oduce carried off the land in 
some fonn. Thus the peculiar feeding habits of 
filants — di.scovered by careful experiments — 
iiave explained those conditions wliich Theorists 
vainly endeavoured to account for by such 
hypotheses as those which the Excretory Theory 
and the Mineral Theory Avere founded on, 
LIFE HISTORIES OF INSECTS INJURIOUS 
TO VEGETATION IN CEYLON. 
By Aba. 
1. Elater Lineatus, Linn. (Sin: Tokka, ©Osarf 
gSi3.) 2. Underside of beetle showing the situa- 
tion of the spine, a. 3. The grub or “ wireworm. ’ 
THE AV'IREWORM. 
The wireAvorms are the Lavvm of several sx^ecies 
of a coleopterous insect f'E'teferJ commonly known 
as the SkixA Jack or Click Beetle from its power of 
regaining its XAOsition when laid on its back by a 
spring or skip, accompanied by a sharp click. 
The name Tohha by which it is known to the 
Sinhalese is also descriptive of this sound or click. 
The leading character of this insect is a strong 
spine (a Fig. 2) situated beneath the thorax, 
Avhich fits at xAleasure into a small caA'ity on the 
uXAper XAart of the abdomen. It is by means of 
this that the beetle is enabled to spring up with 
great force and agility and regain its natural posi- 
tion Avhen laid on its back. 
Wireworms are so called on account of their 
likeness in toughness and shape to a piece of Avire. 
They are A'ery smooth and shining and somewhat 
cylindrical, and perhaxAS resemble bits of wire that 
have been compressed, more than anything else. 
The colour is a sort of ochreous yellow, which 
turns into a darker tint after death. Wireworms 
have three pairs of legs and have also a sucker- 
foot below the tail. 
Miss Ormerod says that “ the egg from which 
this grub is hatched is laid either in the earth 
close to the root of a plant, or between the sheath- 
ing-leaves near the base of the stem. On being 
hatched the grub or ‘wireworm’ eats into the 
stem just above the true root, about an inch below 
the surface of the ground, and sometimes eats its 
Avay ux) the middle of the stalk, even above the 
surface of the earth.” 
“ The Avireworms are said to liA'e five years in 
the grub state, but the length of time XArobably 
depends on the suxjply of food. Where they are 
Avell fed, it is supposed that they only take about 
three years before changing to the x^upa. But 
however this may be, Avith the exception of any 
temxAorary pause in winter (Avhen they go down 
deeper and deeper into the ground as the frost 
increases), they feed voraciou.sly near the surface 
till the time has come to turn into the chrysalis 
(or pupa). Then they go deep into the soil and 
form an earth-cell in Avhich they change, and 
from which the perfect Beetle comes up through 
