30 FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 



Working on from this, M. Robert tried the more extended treatment of paring off 

 the outer bark, a practice much used in Normandy and sometimes in England for re- 

 storing vigor of growth to bark-bound apple trees, and noted by Andrew Knight as 

 giving a great stimulus to vegetation. M. Robert had the whole of the rough outer 

 bark removed from the elm (this may be done conveniently by a scraping-knife 

 shaped like a spoke-shave). 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 moisture around them, or from 

 the maggots being more exposed to atmospheric changes, or any other cause, was 

 not ascertained, but the trees that were experimented on were cleared of the mag- 

 gots. The treatment was applied on a large scale, and the barked trees were found, 

 after examination by the Commissioners of the Institute at two different periods, to 

 be in more vigorous health than the neighboring ones of which the bark was un- 

 touched. More than two thousand elms were thus treated. 



This account is abridged from the leading article in the "Gardener's Chronicle and 

 Agricultural Gazette," for April 29, 1848, and the method is well worth trying in our 

 public and private parks. It is not expensive; the principle on which it acts as re- 

 gards vegetable growth is a well-known one, and as regards insect health it is also 

 well known that a sudden flow of the sap that they feed on, or a sudden increase of 

 moisture around them, is very productive of unhealthiness or of fatal diarrhoea to 

 vegetable feeding grubs. 



A somewhat similar process was tried by the Botanic Society, in 1842, on trees in- 

 fested by the Scolytus destructor in the belt of elms encircling their garden in the Re- 

 gents' Park, London. "It consists in divesting the tree of its rough outer bark, be- 

 ing careful at the infested parts to go deep enougli to destroy the young larvae, and 

 dressing with the usual mixture of lime and cow-dung." This operation was found 

 very successful, and details with illustrations were given in a paper read in 1848 be- 

 fore the Botanic Society. 



Various applications have been recommended, such as brushing the bark of infested 

 trees with coal-tar or with whitewash, in order to keep off the beetle attack. Any- 

 thing of this kind that would make the surface unpleasant to the beetle would cer- 

 tainly be of use so long as it was not of a nature to hurt the tree, and if previously 

 the very rugged bark was partially smoothed it would make the application of what- 

 ever mixture might be chosen easier and more thorough. 



Anything that would catch the beetles, either going into or out from the bark, like 

 coal-tar, would be particularly useful, and probably strong-smelling and greasy mixt- 

 ures, such as fish-oil soft soap, would do much good. 



Washing down the trunks of attacked trees has not been suggested, but, looking 

 at the dislike of the female beetle to moisture in her burrow, it would be worth while, 

 in the case of single trees which it was an object to preserve, to drench the bark daily 

 from a garden-engine for a short time when the beetles were seen (or known by the 

 wood-dust thrown out) to be at work forming burrows for egg-laying. 



The possibility of carrying out the important point of clearing away or treating 

 infested standing trees depends, of course, on local circumstances; but, whatever 

 care is exercised in other ways, it is very unlikely that much good will be done in 

 lessening attack so long as the. inexcusable practice continues of leaving the felled 

 trunks of infested elms lying, tvith their bark still on, when containing myriads of 

 these maggots, which are all getting ready shortly to change to perfect beetles, and to 

 fly to the nearest growing elms. 



Such neglected trunks may be seen in our parks and rural wood-yards all over the 

 country, where, without difficulty, the hand may be run under the bark so as to 

 detach feet and yards in length from the trunk all swarming with white Scolytus 

 maggots in their narrow galleries. 



This bark, with its contents, ought never to be permitted to remain. Where it is 

 loose it may be cleared of many of the maggots by stripping it off and letting the 



