1 Dec., 1897.] QUEENSLAND AGRICULTURAL JOURNAL. 467 
Treatment of the Soil.—The observation of plant life reveals the fact that trees 
already established readily respond to temporary changes of environment, whether 
these changes are related to the condition ot the soil that their roots traverse or to that 
of the air in which they extend their branches. But it is no less true that whatever 
insects are intimately connected with these plants—e.g., as may be Scale Insects 
should they occur upon them—they are affected by these changes of environment also. 
In fact, the alterations that these Seale Insects undergo are more often than 
not, the first indication of anything abnormal in the tree. Thus it was observed 
in many parts of California in May, 1896, that the previously mentioned 
Pernicious Scale (Aspidiotus perniciosus) experienced a remarkable natural mortality 
that could not be explained by the occurrence of any parasitic organism. This 
mortality, that was not attended by any special meteorological conditions, seemed to 
indicate the occurrence of some general abnormal change in the plants that supported 
them. And, again, with regard to the same Scale Insect, it has been observed that 
its northern limit of distribution in the United States of America, does not depend on 
the existence of any unsuitable conditions of climate, but seems to be determined by 
the fact that a special red shale is the prevalent rock, and that this forms a barrier to 
its progeny. Now, this geological feature can only act in this m:nner through the’ 
medium of the plants that grow in it, and support the Scale Insect in question.* 
We trace again the same influence in cases in which generous cultivation of the 
trees of an orchard has induced in them a vigorous condition of growth, that seems to 
react on the Scale Insects, for these—under such cireumstance—many often cease to 
multiply and even commence to die out, whereas, on the other hand, neglect, whilst 
it prejudiciously affects the trees, brings renewed potency to the insects. 
This interaction of insect and plant and the manner in which it is displayed 
suggests, (1) the desirability of maintaining in the orchard good cultivation, using 
that term in its most generous interpretation, as a powerful auxiliary in dealing with 
certain insect pests, such as Scale Insects. It also (2) points to the probability of its 
being found possible to deal with a certain class of insect pests that are closely 
associated with their host plants, as are Scale Insects, by special treatmentof the trees, 
consisting in administering to the soil certain chemical substances calculated to 
determine the existence of changes in them. ; 
With these general considerations relating to that division of the subject 
“Tnsect Foes” concluded, it may be permitted to the writer to proceed to treat 
of ‘Insect Friends.” 
Insect Frrenps. 
Beneficial insects from the fruitgrower’s point of view may be grouped into. two 
classes, viz. :— : : ; 
(1) Comprising those that are directly useful, and such as those that secure 
Hie pollenisation and cross-fertilisation of flowers and consequent setting of 
rut. ee 
(2) Comprising those that are indirectly so—e.g., insects that prey upon 
deleterious members of their class, or are parasitic on or within them. 
Crass I.—The importance to the fruifgrowers of those insects that convey pollen 
from one flower to the other cannot be overestimated. Nature, as has been remarked, 
“abhors self-fertilisation,” and cross-fertilisation that is so desirable, is larg ly effected 
by insects. On the success of this act of cross-fertilisation depends, as you are aware, 
the setting of the fruit that would otherwise often drop to the ground prematurely 
when but just formed. 
Very various are the insects that are included in this class, that embraces both 
those that feed upon pollen exclusively and those that consume nectar. Usually,’ 
however, the important réle that, they enact results from the circumstance that this 
fructifying element adheres to their bodies, and especially to the curious serrated, 
' branched, or plumose hairs with which these are clothed. In others, it becomes attached. 
to their often remarkably formed tongues, and is conveyed from flower to flower, 
whilst these organs are used in exploring one after another for honey. SHive-bees are 
often regarded almost exclusively as flower fertilisers; but the class even includes 
Butterflies, Moths, and Beetles (Cetonias, Small Scarabwids, Buprestidw, Soldier 
Beetles, Malacoderms, Cleride, &c.). Flies are especially serviceable. So are the 
“native bees’? (Zrigoria); the many solitary Apide, the short-tongued bees 
(Andrenidw), and even the social wasps—Polistes, for example. 
Australia is richly endowed with beneficial insects of this class; but, notwith- 
standing this, it will be almost always to the advantage of the fruitgrower to have 
* Cf. Dr. J. B. Smith. Report of the Entomological Division, New Jersey Agr. Exp. Stat., 
1896, pp. 518-9, ; : : 
HI 
