134 ON THE NATURAL HISTORY OF BEETLES 



of the plant, sucked out by means of its sharp proboscis, and ac- 

 cording to the moisture and temperature of the season are its attacks 

 more or less severe. For instance, if, by reason of unpropitious 

 frosty winds in spring the opening foliage of the larch should suffer 

 a check, the trees so affected are more likely to be overtaken by the 

 subtle and interminable exertions of its army of little enemies ; and 

 after such a season the larch trees present a sicklier hue, and have a 

 more viscid feeling, than in a season when their vitality has flowed 

 in an unchecked tide into a rapidly-developed foliage and blossom. 



But while thus presenting the dark side of this picture of Nature 

 in her forest economy, it should also be borne in mind that 

 although a long catalogue of most destructive little insects has 

 been named, there is also a very numerous class of insects which 

 are not only not detrimental to the coniferous or even hardwood 

 trees, but are directly beneficial to them, and especially to the pine 

 tribe, in destroying, and thus keeping in check, other insects 

 which are in themselves destructive, and many of which have been 

 named in the foregoing pages. For example, in the United States 

 of America there exists a small black ladybird, with two red 

 spots on its wing-covers, named Chilocorus bivulnerus, which is 

 remarkably useful in destroying bark hoe and pine-tree scale. 

 Another small ladybird, Exochomus gnexl, which is of a red colour, 

 with two black spots on its wing-covers, and of similar habits, is 

 also frequent, and deserves protective attention. Many of the 

 ichneumon flies destroy whole acres of caterpillars infesting fir 

 trees ; and without the aid of such small predacious and parasitic 

 allies, destructive insects woidd increase to such an extent as to 

 render all forest labour unavailing. It is well known that while 

 there are multitudes of noxious insects devastating whole forests, 

 there are also many useful little animals which by their opera- 

 tions may be said to act as the good genii of all trees, and chiefly 

 of the coniferous tribe. By diminishing the numbers of the 

 injurious, they check their otherwise too rapid increase ; and it 

 Ls the more necessary to state this fact prominently, because, while 

 the planter sees only the damage which is done by the obnoxious 

 creatures, he seldom observes those little insects and their opera- 

 tions which, unappreciated because unseen, are silently, but not 

 the less surely, engaged in counteracting the pernicious operations 

 of the destructive myriads. To encourage and foster the increase 

 of the innocuous classes of insects should be the aim of every 

 one connected with woodland management or plantations. This 



