;h. iv 



ALLIES AND ENEMIES 69 



knowledge of their habits is being gradually acquired, 

 as well as of the remedies necessary to fight successfully 

 against their inroads. Here it is only possible to deal 

 very briefly with them. 



Some insects attack only certain plants, while others 

 are more catholic in their tastes, and some will attack 

 the roots, or the wood, or the leaves or shoots of a tree 

 as the case may be, and some again may, during one 

 stage of their growth, attack the roots, and during 

 another the leaves and shoots, as e.g. the cockchafers 

 (Melolontha). Some weevils (Curculionidae) attack the 

 seeds of trees, while others go for the leaves, and others 

 again attack the cambium zone, and often ultimately 

 girdle the trees and thus kill them. In a report on the 

 forests of Mauritius, 1 one of these is mentioned as doing 

 great damage to forest trees, and the introduction of 

 woodpeckers is recommended. Among other wood- 

 boring beetles perhaps the most injurious are the 

 Scolytidae, which bore galleries in the wood, bark, and 

 bast of trees and injure the cambium zone, the 

 Buprestidae, and the Cerambycidae. As many of these 

 beetles first get an ingress into the forest by attacking 

 unsound and dead trees, it is desirable that all such 

 should be removed as early as possible, as otherwise the 

 insects are liable to turn their attention to healthy 

 trees. A great safeguard is also to keep the forest 

 mixed, as a pure forest, once attacked, is more liable to 

 suffer from wholesale damage. Among the Lepidoptera 

 the caterpillars, both of moths and butterflies, do 

 damage in eating leaves and young shoots. No such 

 damage as that done in Europe by the nun-moth 

 (Liparis Monacha) has been observed by me in tropical 

 forests, probably because they are of a more generally 

 mixed character, and perhaps, partly, owing to the 

 abundance of insectivorous birds or other enemies. 



One of the greatest of insect plagues, not only in 

 tropical but also in extra-tropical countries, chiefly in 

 Asia and Africa, are migratory locusts, the most common 



1 F. Gleadow, Report on the Forests of Mauritius, 1904, p. 57. 



