INSECTS. 



191 



the ground, e.g., Pine Beauty and Pine Span-worm, but not hairy cater- 

 pillars, which only cuckoos eat. When severe attacks are confined to 

 small areas, the migration of caterpillars may be prevented by digging 

 narrow trenches (about 1 foot deep and with perpendicular walls) round 

 the infested portions, and interrupting the leaf-canopy overhead. In 

 these trenches holes, also with clean-cut upright sides, should be made 

 here and there along the sole to catch the caterpillars and lessen their 

 chance of escape ; and similar ditches should be cut within the area 

 isolated. But grease-banding with patent viscous tar is most efficacious 

 for moth-caterpillars that spin down to the ground to 

 moult, or that hibernate under moss, &c. , as the tarry 

 rings prevent them from reascending the stems to 

 feed. Patent tar is only effective while soft and 

 sticky, although its efficacy is dependent on the fact 

 that at least one of the ingredients has a smell so 

 repulsive to caterpillars that they will not cross the 

 ring till it becomes hard and dry. It is therefore 

 essential that the grease-bands should remain sticky 

 throughout the whole of the caterpillar stage of the 

 life of the moth i.e., for at least six to eight weeks 

 without the surface hardening. Before grease-banding 

 the stem needs to be cleared of loose bark, to economise 

 grease and make it adhere closely, a girdle of about 

 4 inches being cleared on the stems with iron scrapers 

 at about breast-height, and care being taken not to 

 damage the soft inner bark. This should be done in 

 winter and early spring throughout areas known to 

 be infested by moth -caterpillars hibernating under the 

 moss or eggs laid on the stems. About the end of 

 March or early in April the rings of patent tar should 

 be applied before mild weather makes the eggs hatch 

 out or the caterpillars resume feeding. The tar can best be laid on with 

 wooden spuds about 1 to 1 inch broad, and smoothed off with other 

 spuds of equal breadth hollowed to a depth of about ith of an inch 

 (Fig. 37), the crop being first thinned to remove superfluous poles or 

 stems likely to attract the breeding moths, and to reduce the cost of 

 grease-banding. 



Eggs can only be collected and destroyed when laid near the ground, 

 and even then many get overlooked. But a daub of patent tar kills egg- 

 clusters of the Gipsy and the Pale Tussock moths. 



The insects chiefly injurious in British woods and nurseries 

 are the following, those that are sometimes very destructive 



Spud and smooth- 

 ing-stick (about 

 \th real size). 



