INSECTS POINTED OUT BY NATURAL HISTORY. 49 



whilst in this state, that we can alone derive any hope of being 

 able to counteract the mischief they occasion. 



The first thing, indeed, to be done, in all such cases, is to 

 ascertain the species of perfect insect which occasions the 

 disease. The experienced naturalist, from an examination 

 in this respect of the worm or larva which he finds devouring 

 the timber, is able not only to ascertain the Order and the 

 Family, but often the Genus, and even the Species of winged in- 

 sect which has produced it. Thus, in the present case, an En- 

 tomologist, by certain characters he would see in the larva, the 

 nature of which his scientific knowledge would point out to 

 him, would be able to determine, in the first instance, that 

 the larva belonged to the Order Coleoptera or Beetles ; by 

 others that it belonged to the Family of Beetles called Pti- 

 nid( 9 from that which possesses their characters in the 

 greatest perfection being called a Ptinus. By other circum- 

 stances he would ascertain that it must be referred to that 

 Genus of Ptinida which bears the name of Hylesinus ; and 

 lastly, from still more minute examination, he would find it 

 to be the species Hylesinus Destructor, so named from its 

 powers of destruction which we have already examined. 



Having thus determined the species, or even the genus only 

 of the insect, it becomes an easy matter to the Entomologist to 

 know the season of its appearance. None of the timber-eating 

 insects, his general knowledge of these animals informs him, 

 remain alive, in their perfect or winged state, throughout the 

 year, and they rarely remain so for more than eight weeks. 

 He finds, therefore, that we may easily ascertain the proper 

 time for cutting down those trees which are so much infected 

 by larvae as to preclude all hope of saving them ; for it would 

 obviously be the height of imprudence not to seize the only 

 opportunity of preventing the annual dispersion of the disease, 

 by destroying the brood of larvae whilst yet in the tree. As 

 soon as the metamorphosis has taken place, as soon as the 

 winged insect has made its appearance, the mischief for the 

 ensuing year is done. Time is thus lost, more trees are in- 

 evitably destroyed, and, what is an evil of far greater magni- 

 tude, the future eradication of the disease is rendered much 

 more difficult. 



Accordingly, from a knowledge of the subject, acquired, 

 virtually, by an investigation of this kind, Mr. Macleay re- 

 commended that the trees in the Parks should be inspected 

 twice every year, first in summer, when the perfect insect 

 is on the wing; and secondly in winter, when those trees 

 which were much infected he recommended to be cut down 

 and burnt, with the larvae in them, or at least fumigated so as 



E 



