ed | i 30 
Entomology. 
DESTRUCTIVE INSECTS LIABLE OF INTRODUCTION TO 
QUEENSLAND. 
By HENRY TRYON, 
Entomologist. 
Ix studying the animal life occurring in any district or. locality, one is leq 
to conclude that it may be grouped in two categories, one of which comprises 
forms indigenous thereto, and the other such as are of exotic origin. Now, 
with regard to the latter the derivation of its members from regions in which 
_ they are cither indigenous, or have previously arrived, is usually accounted for 
by reference to the absence of natural checks—such as mountain chains, waten 
expanses, climatic extremes, &c.; to spontaneous dissemination; to the simul, 
taneous predominance of those conditions of environment that are favourable 
to distribution—afforded by suitable land connections, the persistence of aerial 
or ocean currents of definite trend, &c., the extension of congenial meteoro, 
logical conditions, the fact that special food requirements are forthcoming in 
_ the prospective land of adoption, and, in the case of parasitic or commensal 
animals, the antecedent existence of suitable hosts. ‘hese factors have no 
doubt exercised great influence in determining both the extent and character 
of the immigrant forms of animal life in any region, already prior to the 
portion of mankind dwelling thereon having had any intercourse with outside 
peoples, and no doubt still operate to some extent in the same direction; but 
the changes that they induce in local faune are but gradually effected. It 
seems that they are, however, too exclusively regarded by students concerned 
_ with the problems of geographical distribution. For one cannot afford to lose 
sight of the fact that it is to human intervention, to international commerce, 
and to ordinary trade relations, operating it is true, in conjunction with such 
congenial natural conditions as are above alluded to, that a country is indebted 
_ for many of the forms of life that are most conspicuous in their presence. This 
is especially so as regards insects, and above all, of such as are injuriously 
related to the plants engaging the skill of either agriculturist or horticulturist, 
and which not only impair—or even determine—the vitality of these plants, 
but are also harmful to the crops that they yield or to the manufactured pro- 
ducts that in these originate. This is the explanation of the fact that many 
species of insects included in the above definition that a few years since were 
either unknown, or if known had but a limited range of occurrence, are now 
_ regarded as being cosmopolitan in their distribution. 
But this explanation of the progressive range of occurrence of pernicious 
insects does not apply to their foes. Insects in their native home are almost 
_ without exception to a large extent held in check by natural enemies—such as 
insectivorous birds, predaceous or parasitic members of their class, fungus 
organisms, bacteria, and the diseases occasioned by the presence of these living 
agents. But when such insects have but recently found their way or have 
been transported to new countries, it is seldom indeed that they are so 
victimised, and as a rule only so after a considerable period of time has elapsed 
since their first introduction, and thus they are for a long time more noticeable 
