H2 PROTECTION OF WOODS AGAINST 



growth and active feeding takes place ; the larva often changes 

 its skin or moults several times, and then turns into a pupa 

 or chrysalis. In this stage it remains inactive does not feed, 

 and is often enclosed in a cocoon. Finally, out of the pupa 

 emerges the imago, or perfect insect. The female lays eggs, 

 and a new generation then commences. To thoroughly under- 

 stand the above, the woodman should collect a few common 

 caterpillars from his garden and should place them in a box 

 covered with muslin. If they are kept well supplied with 

 fresh food, the leaves of the plant they were found eating, 

 they will go through all the above stages and can be easily 

 observed. 



Insects do no harm in the egg or pupa stage ; with the 

 majority of species the damage is done in the larva or grub 

 stage, whilst in some cases the perfect insect also does damage. 

 The time which elapses between the egg stage and the fresh 

 production of eggs is termed a generation ; this may be 

 annual, or there may be several generations in the year, while 

 in some cases there is only one generation in several years. 



Most insects are injurious, some injuring forest trees, others 

 agricultural crops. Only very few are useful in forestry. The 

 damage done depends on the species, and may be very slight 

 or so bad that large areas of woods are destroyed. Injurious 

 insects may do damage by eating leaves, flowers, or fruits of 

 trees, by gnawing the roots or by boring in bark or timber. 

 Some attack dead trees only and are therefore not so injurious 

 as those which attack and kill healthy trees. 



As a general rule conifers suffer from insect attack more 

 than broad -leaved trees. 



There is no doubt that a far larger amount of damage is 

 done by insects than is generally suspected, and it is a very 

 necessary part of the woodman's duties, too often neglected, 

 to keep a sharp look out for insect attacks and to take such 

 measures as is possible against them. 



Prevention is always better than cure, and danger can be 



