AND OTHER INSECTS WHICH INFEST CONIFEIUE. 129 



destroying insects, arises from the permanent disruption between 

 wood and bark caused by the innumerable earwigs, spiders, flies, 

 wood-lice, &c, which take possession of the cavities, allured by the 

 exuding sap, no less than by the shelter which the loose bark affords. 

 "We have in Scotland little conception of the damage done to forests 

 by these insects. Numerous instances are on record of the extent of 

 their prevalence and ravages. In Germany and Austria, for example, 

 it is stated that 80,000 of the Bostrichus typographic have been 

 found in one tree ; and so great is the vitality of this little pest 

 that nothing short of fire will destroy it. In the beginning of last 

 century it was unusually abundant in the Hartz forests, and con- 

 tinued in immense numbers for several years — first in 1757, when 

 its ravages were very severe; again in 1769 and in 1783, when the 

 total number of its victims in the forests mentioned amounted to 

 1,500,000; and the indirect result of its destructive agency was 

 that the industrial pursuits of the surrounding country were seri- 

 ously crippled, and in some localities actually suspended. Cold and 

 wet seasons, however, in 1784 and in 1789, tended greatly to diminish 

 its numbers. In 1790, however, it reappeared, and again in 1796, 

 when serious fears were entertained for the safety of the few remain- 

 ing fir trees, which the ravages of former years had spared.* 



But in addition to the insects which infest pines by burrowing 

 under the bark, there is an equally numerous and destructive host 

 whose ravages are carried on with similar precision in other ways, 

 by attacking the foliage or the roots of the tree. The well-known 

 substance termed " honeydew " is said to be the secretion of a 

 species of Aphis. The larch in this country is infested with an 

 aphis whose wax-like "cottony" filaments are well known, and are 

 often so abundant as to whiten the entire tree, and ultimately (if 

 not removed or checked) to cause its destruction. Then again, 

 there are other deposits caused by the Aphidte, which, although in 

 themselves very beautiful, resembling as they do, when their 

 mechanism is closely examined, fruit, blossoms, flowers, &c, are 

 yet, if allowed to spread to undue proportions, full of danger, and 

 sometimes convey total destruction to the tree. These deposits 

 refer to the secretions of the Aphis abictis. The larvaa of several 

 moths also attack fir and other trees by destroying their foliage, 

 viz., DendroUmus pint, Psiluria moriacha, Achatia pinip&rda, 

 Bupcdus piniarius, Orthotcenia turionana and resinetta, &c. The 

 three species of saw-fly (Lophyrus pini and rufics, and Pamphilius 

 * Latreille, Hist, Nat. ix. 194. 



