CHAP, xiv.] Insect Enemies 327 



in search of food. The so-called nests of caterpillars of the 

 Lackey moth ( Gastropacha neustria) may also easily be crushed 

 or burned, as well as the cocoon-like clusters containing those 

 of the Processionary moth ( Cnethocampa processioned]. 



When the attacks are severe but confined to small areas, 

 the migration of the caterpillars to neighbouring crops may be 

 prevented by isolating the infested portions by means of narrow 

 ditches a method which, of course, can only be efficacious 

 if the leaf-canopy overhead be also interrupted. The deepest 

 ditches are required for the large Pine moth, when they are 

 made nearly 2 feet deep; but, in general, a depth of 12 to 

 15 inches is sufficient, care being in every case taken to ensure 

 the walls being cut perpendicularly, whilst holes should be 

 made here and there (also with clean-cut, upright sides) along 

 the sole of the ditch to catch the caterpillars and lessen their 

 chance of escaping up the sides. It is also advisable to cut 

 several traverse ditches within the area thus isolated, in order 

 to make the work of extermination as complete as possible. 



One of the great lessons taught by the recent ravages of the 

 Spruce moth in Bavaria third in importance only (i) to the 

 great advantages derivable from the formation of mixed woods, 

 and (2) to the necessity for taking active steps against injurious 

 insects whenever there is the slightest sign of the balance of 

 nature having been disturbed in any such manner as to permit 

 of their abnormal frequency is the efficacy of forming rings or 

 girdles of patent glue * or viscous tar around all stems in infested 

 tracts, for the purpose of hindering caterpillars from ascending 

 to their feeding-grounds on the foliage, or, if once up, from 

 descending the stems for the purpose of entering into the pupal 

 state of rest, or for any other purpose. It has thus become by 

 far the most efficacious method of combatting bad attacks 

 of dangerous enemies like the Pine and Spruce (Nun) moths. 



1 Leim (Ger.) means glue, and not lime, as was the incorrect translation 

 given in the Foreign Office report on The JVun Moth (Liparis monacha] in 

 Bavaria, published in 1891. 



