502 QUEENSLAND AGRICULTURAL JOURNAL. [1 June, 1898. 
By the term “nursery stock” is intended not only entire plants, but also 
cuttings, grafts, and buds; the last being a prolific and often unsuspected 
source of further infestation, the young scales occurring ensconced within them 
when the trees from which they have been derived are apparently free. 
The list of the food-plants of the Pernicious Seale, given on page 495, is 
suggestive of the possibility of its being introduced into new countries, or 
further disseminated in those in which it already occurs, on other than deciduous 
fruit trees, especially by the agency of members of the order Rosacew. Amongst 
the number may be mentioned linden, spindlewood (Huonymus), Spirea, rose, 
hawthorn, cotoneaster, Acacia, elm, alder, weeping willow, on all of which the 
occurrence of the insect has been definitely ascertained. 
‘The fact that the insect occurs upon trees in a dormant condition at the 
season of the year best adapted for traffic in orchard trees generally favours its 
distribution by the latter. 
The ordinary deciduous fruit trees are, however, the principal vehicles on 
which it is introduced and disseminated. Judging also from the condition of 
fruit occasionally received from New South Wales, the insect must be quite as 
frequently transported from district to district in Australia by this means as 
in the United States. 
INSPECTION, 
From the foregoing description of the insect and its mode of occurrence, 
badly or even moderately infested plants may be detected and so dealt with. 
Tt may happen, however, that one or two scales only (and what are the chances 
of one or two of these minute insects occurring in a bundle of fruit trees being 
detected) may occur upon a plant, and these be still immature; but the possi- 
bilities resulting from even this limited infestation are serious to contemplate 
(vid. p.499). Further, a but slightly infested tree may have provided young 
for the contamination of previously clean ones, though these young cannot by 
reason of their diminutiveness yet be discerned upon them. Accordingly the 
injudiciousness of pronouncing trees on which Perticious Scale may be expected 
to oceur clean after inspection only, is very evident. This ultimatum—if 
forthcoming at all—should result from a knowledge that they have been 
shortly previously subjected to an effectual process of disinfection, preferably 
under the direction of one called upon to deliver it. 
NATURAL CHECKS AND NATURAL ENEMIES. 
Though, as L, O. Howard has pointed out, the Pernicious Scale belongs to 
a class of insects that are facultative cosmopolites—or adapted to becoming 
-yery generally naturalised over the earth’s surface—it would appear that 
special conditions of climate may oppose an obstacle to its natural merease, or 
indeed even to its permanent establishment in some regions. ‘The United States 
have been mapped out by an American meteorologist into several climatic 
districts or life-zones, and the above-mentioned entomologist has shown that 
the Pernicious Scale would appear to have become established there in the 
so-called austral life-zones only. And the application of this discovery to its 
distribution in the State of Massachusetts he showed, at a meeting of the 
Massachusetts Horticultural Society, in 1896 (vid. IX., p. 85). With regard, 
however, to Queensland and Australia generally, sufficient data have not been 
accumulated to admit of profitable speculation as to the ultimate effect of climate 
on the prevalence with which the insect will attack vegetation in particular 
districts being entered upon. 
There are, however, other natural checks, consisting in the occurrence of 
infectious parasitic diseases and predaceous insects—both parasitic and others— 
that would appear to be as operative here as in the United States of America. 
' With regard to the latter region, these have been dealt with by L. O. 
Howard (X., pp. 51-5, and VIIL., pp. 289-90) and other writers, more especially by 
Dr. J. B. Smith (XIL., pp. 517-540), and need not be further referred to on this 
oecasion, though the desirability of procuring if possible the establishment of the 
parasitic and predaceous insects alluded to in Australia may be insisted upon. 
