insects seem to be almost omnivorous, but most attack only a 
certain plant and those most nearly allied to it, unless the food 
supply runs short when they fall upon the nearest plant that 
they can eat, as happened recently in Selangor when cater- 
pillars, which had been feeding on castor oil plants grown near 
coffee, having devoured all the castor oil plants, fell upon the 
coffee bushes and commenced to eat them. 
A pest sometimes after being easily kept within bounds for 
years, may, for no clear reason, suddenly on some year, become 
so abundant that it is quite uncontrollable, perhaps almost en- 
tirely disappearing on the following year, and not reappearing 
for a long period, ihe cause of this is not very clear, and it is 
Usually attributed to variations in the weather, or the accidental 
absence of some enemy of the pest. During the time of the 
great plague of the Coffee-caterpillar in Selangor, 189S and 1899, 
I noticed that several other kinds of caterpillars were extra- 
ordinarily abundant, notably that of the small yellow butterfly, 
7 erias , which feeds on Albizzia. It is quite possible that in this 
case some abnormality in the weather proved either exceptional- 
ly suitable to these insects or exceptionally unsuitable to some 
particular enemy, but observations on these points are still re- 
quired. The blights (Coccidai) and aphides are very apt to be 
more virulent when the weather is damper than usual. 
Plants that are sick or ill-nourished suffer more from insect 
pests than those in a healthy condition, and it is wonderful to 
note how manuring a tree will often cause the disappearance of 
blights which have resisted tuba water, tobacco or other insecti- 
cides. This shows that the miserable appearance of the tree 
was not due to the attacks of the blight, but that the blight per- 
sisted on the plant on account of its sickness. The same thing 
often happens even in caterpillar attacks, the trees which are 
sick have no recovering power and fail to throw out fresh leaves 
after the destruction of the old ones in time to save its life. 
In some regions, trees which would otherwise thrive are practi- 
cally kept out of cultivation by insect pests. The Mango in the 
south of the Peninsula is an example of this. It is attacked by so 
many insects that it really has no chance. The w r orst of these is 
a boring caterpillar which burrows up the branches, which soon 
die and fall off. It is interesting to note that the only trees not 
badly attacked here are those growing over water. It has long 
been known in Europe that ponds underneath trees often keep 
off insects, especially beetles and moths, which are perhaps afraid 
to cross, the water or if they do, fall in and are drowned. 
Groups of Insects. 
A short summary of the groups of insects may be of ose in 
enabling a cultivator to judge whether an insect found on or near 
his plants belongs to an injurious group or not, as in many cases 
the enemy of the pest is mistaken for^the enemy of the plant. 
Lepidoptcra . — Butterflies and moths are only injurious here in 
the caterpillar state. The caterpillars are soft bodied, often 
