450 
THE TEOPICAL AGRICULTUiaST. 
[Jan. 2. \m. 
tliafc the cacao trees were almost exempt from attack, 
nor did the tea appear to suft'er to any great extent. 
My visit on November 8 was most fortunately 
timed, as I found tlie insects pairing, and was shown 
several small patches of ground where they were 
congregated in vast numbers, evidently for breeding 
purposes. In one such patch, about four yards 
i-quare, the insects had comjiletely covered the 
gromid tni'ee or four inches tliiek, and had partly 
filled up a drain that crossed the place. It was a 
most remarkable sight, and the noise of rustling 
wings and low chirruping, could be distinguishtd 
from a considerable distance. The air, too, was 
charged with the acrid smell produced by the insects. 
0)1 examination of the ground it was evident that 
the impregnated females were freely depositing their 
eggs here. The soil was closely pitted with holes, 
each about three inches deep and half an inch in 
diameter. In these holes masses of eggs were de- 
posited encased in a frothy yet firm covering, and 
above them the whole was filled up with the same 
porous matter. The eggs when first laid are pale 
yellow, but gradually darken to a reddish Ijrown or 
purplish colour. The porous matter in which they 
are enveloped has a pinkish tinge. 
The holes are excavated by the abdomen of the 
female insect, which is enormously distended with 
eggs. The normal length of the entire insect is 
only 2i in., but during oviposition the abdomen 
alone attains a length of about S inches. 
I was unable to determine the exact conditions 
that regulate the choice of the breeding sites. Thoy 
appeared to be selected quite at haphazard, but all 
were more or less shaded )jy the cacao trees. The 
nature of the soil did not appear to exercise much 
iniiucnco in the choice, for the eggs were equally 
distributed in loose sand, stiff clayey soil, and 
ordinary loam. In one instance the pits had been 
excavated in the hard beaten earth of the footpath. 
It is very evident that the most favourable time 
to attack the pest is when the locusts are crowded 
together on these breeding grounds. They may 
here be collected and destroyed with the greatest 
ease {as they make no effort to escape), and at a 
very small cost, by sweeping them into sacks, which 
may then be sunk under water for three or four 
hours till the insects are dead. Hags made of coir- 
matting are . most suitable, as they admit the water 
readily. A trial bag filled at ojic of these places 
of assembly was found to weigh lOG lb. As a single 
insect weighs on an average just one-eighth of an 
ounce, this bag must have contained about 12,800 
individuals, allowing C lb. for the weight of the 
bag. From this one spot 20 such bags could have 
been filled without any difficulty. 
After repeatedly clearing away and destroying 
the insects till they cease assembling there, the 
ground on the immediate spot and for a short 
distance all round should be broken up to a depth 
of G inches and quicklime turned in. This will 
ensure the almost complete destruction of the brood. 
The mere breaking up of the earth would probably 
of itself prevent the greater number of the eggs 
from hatching out, by exposing the egg-masses to 
the drying action of the air and to the attacks of 
birds and predatory insects such as ants and beetles, 
which would readily feed upon them. 
The locusts appear to be confined to a limited 
area at present, and could be practically exter- 
minated in the course of one or two seasons. The 
fully-grown insects die off after pairing and deposit- 
ing their eggs, so that the most important part of 
the work is the destruction of the eggs, A certain 
number will no doubt escape and appear later on 
as small wingless grasshoppers. The breeding 
grounds should be carefully watclied, aad if the 
young locu.'^ts should appear in any nuinbcrK they 
may be destroyed by driving ihcm into trenches 
and covering them with earth which should be well 
stamped down above them. 
I am now carrying out experiments to aficertain 
tlie time that elapses between the laying of the eggs 
and the birth of the young locusts. The epgs of 
an allied species in India have been proved to batch 
out in about four wee ks, and the iusectb were fully 
grown in three mouthb' time. It is very probable 
that there are two or more broods of the spotted 
hicust in the course of the ^-ear. The young locustb 
were noticed on the above nieutioued estate in 
Api'ii. If the life-cycle of this locust is similar to 
that (<f tlie Indian species, these young instetn 
would have cnurgcd from eggs laid in March, the 
parditB of which would have resultetl from the 
previous October-November breeding season. 
There may possibly be a third breeding period in 
July-August. On the other hand, it is possible that 
only one brood occurs in the year, the eggb laid in 
October-November remaining underground until the 
following .i\pril. This should be made a matter 
for careful observation. 
From inquiries on the spot I learned that the 
locusts were first noticed on that estate in large 
numbers in June, 1897. Thejk are baid to have 
died in thousands and disnpjKared when the north- 
east rains came on, and to have re-ajjpeared in 
March or April of the present year in greatly in- 
creased nniulxrs and over an extended area. It is 
probable that ilie great mortality noticed in the 
north-cast monsoon occurred in the ordinary course 
of events, after the pairing of the insects and the 
deposition of the eggs. 
These locusts seem to bo exempt from the attacks 
of birds, lixards, and other predatory animals, being 
protected by an acrid frothy fluid which they can 
discharge when irritated, both from the mouth and 
from pores on each side of the thorax. 
Baits composed of bran poisoned with arsenic 
were tried, but though a few of the insects were 
found feeding upon the bait, it did not prove suffi- 
ciently attractive to repay any extension of the plan. 
Nor do I consider that any other measures than 
the collection of the living nisects on the breeding 
grounds and the destruction of the eggs are, under 
existing circiuiistances, necessary. 
The following more important points mav be 
repeated : — 
At certain sea.sous of the year, of which October, 
November has been found to be one, the locusts 
assemble in vast numbers upon lunited patches of 
ground where the females — still accompanied by the 
males — bury their eggs in pits about 3 inches deep. 
A watch should be kept for these places of assembly, 
and natives should be encouraged to report the 
occurrence of breeding grounds upon their gardens 
or any waste laud in the neighbourhood. The 
locusts should be collected and destroyed from day 
to day as they collect on these spots. As soon as 
they cease assembling, the ground should be dug up 
and well mixed with Unslaked lime. Upon the 
appearance of any swarm of young locusts, trenches 
should be dug, into which the insects can be swept 
and afterwards buried. 
Attention to these j)articulars cannot fail to result 
either in the practical extermination of the insects 
iu the locality, or hi so reducing their numbers 
that they can do little or no damage. 
E. E. Geeex, 
Hon. Govt. Entomologist. 
JOHN C. WILLIS, 
Director, Eoyal Botanic Gardens, 
Peradenij'a, November 2d,'l696. 
