184 THE PROTECTION OF WOODLANDS. 



B. Witk incomplete metamorphosis. 



V. Hemiptera ("half-wings") or Bugs, Plant-lice, and Scale- 

 insects, &c., having 2 pairs of wings, either all membraneous 

 (sub-order Homoptera, with fore and hind wings similar, 

 or Plant-lice and Scale-insects, &c.) or else the front pair 

 leathery at base and opaque (sub-order Heteroptera, with 

 fore and hind wings different, or Bugs) ; mouth formed into 

 a snout (proboscis) for sucking and piercing. 



VI. Orthoptera (" straight -wings") or Grasshoppers and Crickets, 

 having 2 pairs of wings, the front pair narrow, leathery, and 

 with straight veins, the hind pair fan-shaped ; mouth for 

 biting. 



VII. Neuroptera ("nerve-wings") or Dragon - Flies and Lace-wing 

 Flies, having 2 pairs of wings with a network of veins ; mouth 

 for biting. 



VIII. Thysanoptera ("fringe- wings") or Thrips, small insects having 2 

 pairs of very narrow wings fringed all round with fine hairs ; 

 mouth for biting, but weak. 



C. Without metamorphosis. 



IX. Aptera ("without wings") or Springtails, &c., small insects 

 having no wings, but either a locomotive apparatus like a 

 spring beneath, or a process like a tail ; mouth for biting, but 

 weak. 



In our woodlands beetles and moths are by far the most 

 destructive insects, then sawflies and plant-lice. In beetles 

 the structure and the different segments of the adult are 

 distinguishable in the pupa, but in moths they are still 

 indistinguishable. No insects of the orders Orthoptera, 

 Neuroptera, Thysanoptera, or Aptera damage trees, while many 

 of the Neuroptera are useful by preying on the injurious 

 kinds of insects. 



Damage by Insects. Conifers, and especially Pine, Larch, and 

 Spruce, are usually much more attacked than broad -leaved trees ; and the 

 attacks are generally far more destructive, owing to their much smaller 

 reserves of starchy and nitrogenous substances as compared with broad - 

 leaved trees. Oak, Beech, Poplar, and Willow are more attacked than 



