WHITE MARKED TUSSOCK MOTH AND ELM LEAF BEETLE 13 



quently more eggs are usually deposited on trees which have been 

 defoliated earlier in the season than upon others. 



Badly infested trees are therefore very likely to lose two crops of 

 leaves in a season and may possibly have their third seriously marred 

 by this pest. The second brood of grubs completes its growth 

 about the middle of August, beetles appearing the latter part of the 

 month, and if there is an abundant supply of fresh leaves, a third 

 generation may appear in considerable numbers. This last brood 

 more frequently occurs in near-by trees which have not been 

 severely injured earlier in the season. 



Natural enemies. This leaf feeder is subject to attack by a 

 number of natural enemies, most of which, however, are of compara- 

 tively little importance in keeping it in check. The common garden 

 toad will devour many beetles, and the much despised English 

 sparrow also feeds upon these insects to some extent. Several 

 predaceous insects prey upon this pest to a certain degree. 



Remedial measures. The secret in controlling this insect lies 

 in understanding thoroughly its life history and appreciating the 

 vulnerable points. A thorough spraying with an arsenical poison 

 early in the spring, when the beetles begin to feed, is most effective 

 in preventing breeding, as the parent insects are destroyed before 

 they can deposit many eggs. Fortunately the beetles are rather 

 local in habit and as a consequence individual trees or groups of 

 trees may be protected to a very large extent even if there are neg- 

 lected ones in the near vicinity. The local spread of this pest is 

 slow and this should be taken advantage of to the greatest possible 

 extent by keeping the insect in control wherever it occurs, even 

 though the infestation be a small one and the present injury of com- 

 paratively little importance. It is a mistake on the part of local 

 authorities to wait till this enemy of the elms has become well estab- 

 lished and destructive before repressive measures are undertaken. 



The grubs feed almost exclusively on the under surface of the 

 leaf, rarely occurring upon its upper side. The first injury is usually 

 on the upper more tender leaves, hence there is great need of spray- 

 ing the tops of the trees, and in order to kill the destructive grubs it 

 is essential that the poison be thrown on the underside of the foliage. 

 Spraying with an arsenical poison for the destruction of grubs is 

 satisfactory only when the application is early, as it is hardly advis- 

 able to spray for this insect when the grubs are nearly full grown, 



