10 INDIAN FOREST INSECTS 



insects so formed commit serious damage to the bast and wood of the 

 roots, main stem, and branches of the tree. To mention but a few 

 instances, members of the famihes Siricidae (Hymenoptera) ; Buprestidae 

 (p. igo), Cerambycidae (p. 268), Scolytidae (p. 457) (Coleoptera) ; Cossidae, 

 and ArbeHdae (Lepidoptera), do such damage either in their larval or 

 imagine stages. Other species live in the bast or interior of the smaller 

 branches and twigs : Scolytidae; Pyralidae (Lepidoptera), for instance ; whilst 

 others again feed on the leaves or needles of the tree : sawflies (Tenthredinidae); 

 Chrysomelidae (p. 253), Curculionidae (p. 393) (Coleoptera); Lymantriidae, 

 Noctuidae, Pyralidae (Lepidoptera). Finally, other biting insects destroy 

 the flowers or fruits : Chrysomelidae, Cantharidae (p. 246), or tunnel into 

 the seeds, as for example members of such families as the Bruchidae (p. 250), 

 Curculionidae, Scolytidae; Pyralidae, Microlepidoptera (Lepidoptera). 



(6) Sucking Insects.— The powers of the sucking insect to damage the 

 tree are somewhat more restricted, since it is unable to attack such 

 portions as are coated with thick bark, save where it can obtain ingress 

 to the bast layer through wounds, a fruitful source of attack. The area of 

 the tree open to attack is, however, still of very considerable extent, 

 consisting as it does of the whole of the crown and the smaller 

 roots ; and, of course, seedlings and young saplings are subject to 

 injury in every part. In the case of some trees, all the conifers for 

 example, the injury possible from the sucking insect is of very considerable 

 extent. 



The younger roots are subject to the attacks of one of the worst families 

 of sucking insects, the plant lice or Aphidae (Rhynchota). The roots may 

 also be galled and consequently weakened under the attacks of Chalcidae 

 (Hymenoptera), Aphidae, and Coccidae (Rhynchota). 



The stems, branches, twigs, and leaves, are subject to direct attack 

 by tapping or suction by Aphidae and Coccidae. Or, again, galls may 

 be produced on any of these parts by Chalcidae, Curculionidae, Aphidae, and 

 Coccidae. 



Similarly the flowers and seed may be either directly tapped by the 

 chalcid, aphid, or coccid family, or they may be indirectly affected and 

 the seed aborted or rendered barren by the insidious tapping of the sap of 

 the flower-bearing twigs by members of these families. 



2. The Method of Growth of the Tree and Nature of its Parts. 



This section maybe prefaced with the remark that in nature the balance 

 between the tree and the insect is held fairly even. A primeval forest 

 alwa\ s contains a number of sickly and dying trees, which provide suflicient 

 food for the insects who prey upon the particular species of tree. It is 

 usually, not always, only when man interferes with nature's balance of 

 power that serious insect invasions in the forests are experienced. This 



