30 FIFTH REPORT OF THE ENTOMOLOGICAL COMMISSION. 
Working on from this, M. Robert tried tin* more extended treatment of paring off 
the outer bark, ■ practice much used in Normandy and sometimes in England for re- 
storing vigor ol growth to bark-bonnd apple trees, and noted by Andrew Knight as 
giving a great stimulus t<» vegetation. M. Robert had the whole of the rough outer 
bark removed from tbe elm (this may be done conveniently by a scraping-knife 
shaped like a spoke-shave). Thi§ operation caused a great flow of sap in tbe inner 
lining of the bark (the liber), and the grubs of tbe 8ooljftut 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 
tbe maggots being more exposed to atmospheric changes, 01 any other cause, was 
not ascertained, but the trees that were experimented on were cleared of the mag- 
jmUs. 'flic treatment was applied on a large scale, and the barked trees were found, 
att.r 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 "J'J, 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 incre, 
moisture around them, is very productive of unhealthiness or of fatal diarrhu-a to 
vegetable feeding grnbs. 
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 enough 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 Botauic 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 importaut 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, uith their hark 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 truuk 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 
