CHAP, xiv.] Insect Enemies 323 



to promote the increase of their natural enemies, most par- 

 ticularly amongst the class of insectivorous birds. These are, 

 however, naturally of somewhat infrequent occurrence in dark, 

 sombre coniferous woods as compared with broad-leaved and 

 mixed crops. And amongst these insectivorous birds there is 

 none which deserves so much encouragement as the Starling 

 (Sturnus vulgaris\ for whose convenience and protection 

 nesting-boxes should be hung or nailed up in the woods, to 

 protect their eggs and young against cuckoos, cats, and other 

 enemies. Since the recent devastations of the Spruce moth in 

 Bavaria (1890-1892) there have been many thousands of such 

 starling-boxes distributed throughout the State Forests in order 

 to promote the breeding of these most useful birds. 



Exterminative Measures. 



As previously stated, endeavours must be made to put an 

 end to every abnormal increase in the appearance of any noxious 

 insect, before it acquires the power of reproducing itself in count- 

 less swarms. This requires some knowledge of the appear- 

 ance, habits, and life-history of injurious species generally. 

 It also involves constant attention being paid to all areas where 

 plantations or fellings have been recently made, or where 

 damage has occurred from wind or snow, as well as to all sickly 

 and backward crops, which might easily develop into extensive 

 breeding-places. The frequent revision of Pine and Spruce 

 woods is indeed an absolutely indispensable measure. The 

 discovery of noxious insects may take place by many different 

 kinds of observations. Bore-holes on the stems, bore-dust, or 

 cobwebs, or drops of resin on the bark or at the foot of poles 

 or trees, all indicate their presence in the stems of standing 

 crops ; whilst excreta or damaged foliage along paths and in 

 the ruts of cart-tracks, and a gradual thinning of the foliage, 

 indicate the presence of moth-caterpillars in the crowns of the 

 trees. Even before these last signs become distinct, the 



Y 2 



