218 ELM. 



the ScolijtKs 'prnni lie had observed " burrows less than one 

 inch long, some of which, containing a few eggs already laid, 

 had been abandoned uncompleted by the beetles, apparently 

 on account of the presence of a fluid which must have been 

 sap, as no rain had fallen to account for it." — (Ent. Mo. 

 Mag. ; Illus. Brit. Ent. ; &c.) 



Peevention and Eemedies. — One method of remedy which 

 appears to be worth consideration is that adopted with great 

 success in France by M. Eobert, after careful observation of 

 the circumstances which stopped the operations of the female 

 beetle when gnawing her gallery for egg-laying, or which dis- 

 agreed with or destroyed the maggots, and is based in part 

 on similar observations of the effect of flow of sap to those 

 noticed in England by Dr. Chapman. 



It appeared, on examination, that the grubs died if they 

 were not well protected from the drying action of the air ; on 

 the other hand, if there was a very large amount of sap in 

 the vegetable tissues that they fed on, this also killed them, 

 and it was observed that, when the female was boring through 

 the bark, if a flow of sap took place she abandoned the spot 

 and went elsewhere. It was also noticed that the attack 

 (that is, the boring of the galleries which separates much of 

 the bark from the wood) is usually under thick old bark, such 

 as that of old Elm trunks, rather than under the thinner 

 bark of the branches. Working on these observations, M. 

 Eobert had strips of about two inches wide cut out of the 

 bark from the large boughs down the trunk to the ground, 

 and it was found that where the young bark pressed forward 

 to heal the wound, and a vigorous flow of sap took place, 

 many of the maggots near it were killed, the bark which had 

 not been entirely undermined was consolidated, and the health 

 of the tree was improved. 



Working on from this, M. Eobert tried the more extended 

 treatment of paring off" the outer bark, a practice much used 

 in Normandy and sometimes in England for restoring vigour 

 of growth to bark-bound Apple-trees, and noted by Andrew 

 Knight as giving a great stimulus to vegetation. M. Eobert 

 had the whole of the rough outer bark removed from the Elm 

 (this may be done conveniently by a scraping-knife shaped 

 like a spokeshave). This operation caused a great flow of sap 

 in the inner lining of the bark (the liber), and the grubs of 

 the Scolytus beetle were found in almost all cases to perish 

 shortly after. Whether this occurred from the altered sap 

 disagreeing with them, or from the greater amount of mois- 

 ture round them, or from the maggots being more exposed to 

 atmospheric changes, or any other cause, was not ascertained. 



