Systematic Course, 31 
That these are merely typical examples of what is likely to go on 
generally is indicated by the fact that the injury by weevil to stored 
wheat and rice in India has been estimated at several millions of 
rupees annually. , The fruit of the mango, again, in Bengal is very 
largely attacked by a weevil whose larva lives in the pulp and thus 
renders the fruit toa great extent wneatable, In the case both of 
seed and of fruit attacked by weevil, the hole made by the grub in 
cutting its way into the interior isso small that it is very difficult 
to detect injury until the beetles begin to emerge. 
Wheat which is kept tightly packed in village pits, where the air 
is almost completely excluded, is found to escape attack. Seed also 
kept in a closed receptacle of any kind with a little bisulphide of 
carbon or naphthaline is also said to avoid injury. No satisfactory 
method of dealing with the mango-weevil has yet been discovered, 
but it may be noticed that in the United States, where plums suffer 
to some extent from an insect with very similar habits, spraying the 
trees with washes made of an arsenical poison known as London 
purple, in the early part of the season, has been found effective, 
This treatment would only be practicable under exceptional cir- 
cumstances in India, and would always be somewhat dangerous, as 
London purple is excessively poisonous to all animals. The students 
should examine and sketch a few typical Curculionide from the 
Museum collection. 
Scolytida (Bark borers).—This family of tetramerous beetles comprises 
numerous species which are destructive to forest trees in India. 
Conifers in particular are specially liable to attack. The beetles are 
small obscure creatures, which often have much superficial resemblance 
to the Ptinide. They can, however, be distinguished from Ptinide 
beetles both by the structure of the tarsi and also by the fact that 
their larvee are without legs. 
The female beetle usually bores atunnel in the bark and lays her 
eggs at intervals along it. The larve on emerging from the eggs 
tunnel in all directions away from the original burrow, often travel- 
ling immediately between the bark and the wood, and leaving behind 
them apattern of very definite character. When full grown they 
transform into pups, in the burrows, the beetles afterwards cutting 
their way out through the bark. Several generations are likely to 
be gone through in the course of the year. 
Like other wood-boring insects the Scolytide are believed to prefer 
for their attack trees whose vitality has been impaired by injury or 
Forest fires and the attack of leaf-feeding caterpillars are 
probably fruitful sources of the increase of bark-borers in Indian 
. forests. In cases where Scolytids have become very numerous and 
where damaged trees are not available, they are said to attack 
disease. 
