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other pests with nursery stock. It is probable that in the present 
instance the beetle may have been present at Kew in small 
numbers for many years and escaped detection until the sudden 
enfeeblement of the host plants from another cause, made it 
possible for the beetles to increase rapidly in numbers and kill 
thé branches. It is well known that the elm-bark beetles may | 
- be present on healthy trees for many years causing little harm, 
whereas, after the weakening of the trees by other agencies, the 
beetles rapidly increase in numbers and kill the trees. 
The rapidity with which a disease is able to spread on closely 
cropped ground emphasises the necessity for gardeners, foresters, 
and farmers, to be constantly on the alert. Diseases, whether 
of fungus or insect agency, usually appear in the first instance on 
single plants or on limited areas and the application of a wash 
or burning a few plants at the outset may prevent an epidemic 
that would do incalculable harm at a later date were they 
neglected. The supply of clean nursery stock is also of vital 
importance in the control of disease and care should be taken 
to clean any infected stock before it leaves the nursery. 
The appearance of the thuya bark beetle at Kew affords 
a good opportunity of directing attention to other bark beetles 
found in the gardens and on the invitation of the Director, 
Dr. Munro has prepared the following list, with drawings of the 
galleries of some of the principal genera found in the sap-wood 
The discovery of the bark beetle Phloeosinus thujae, Perris, 
in the Royal Botanic Gardens, by Mr. Dallimore, has called 
attention to the Kew bark beetles generally. No list of these 
has so far been- published and except for an exotic species, 
Xyleborus morigerus, Bland., recorded by Pearson in B. 
‘Additional Series V, there is no mention of bark -beetles in the 
Kew fauna lists. The following list therefore, based on observa- 
tions made by the writer during the last two years and on material 
iat by Mr. Dallimore, has been prepared at the Director’s 
request. 
destructor, (Large Elm Bark Beetle). —This 
species is abundant in Sa on elms. It increased in numbers 
during 1921 probably owing to the favourable conditions produced 
by the drought. 
Scolytus m multistriatus, Marsh, (Small Elm Bark Beetle).— 
This species is found together with S. destructor but is less common. 
Both these species are accompanied by the Elm Bark Weevil 
(Magdalis armigera, F.). 
Scolytus pruni, Ratz., (Large Fruit-tree Bark Beetle).— 
A few specimens have occurred in the Director’s Orchard and 
one brood was reared on cherry laurel (Prunus Laurocerasus), in 
Cambridge Cottage Garden in 1921, in a hawthorn log in 
Queen’s Cottage Grounds, 1922, and on Prunus Padus in the 
Upper Nursery, 1922. 
