being crushed or shaken off the plants, and falling a prey to ants, &c. 

 The consequence is that insect life can only develope freely at such spots 

 which accidentally escape invasion. Another well-known fact greatly 

 assists in localizing species, namely, that most females of many species 

 do not quit their own birthplace voluntarily, for as soon as impregnation bas 

 taken place they deposit their ova at the next suitable plant or other 

 place and die. No great wonder, therefore, localities of exuberant insect 

 life should remain isolated. Now, the chances are greatly against the 

 escape of such localities from invasion for any length of time wherever 

 cattle are depastured ; thus, instead of extending, which is a slow pro- 

 cess at most times, they gradually contract, and at last become extinct, 

 perhaps in one season, and their inhabitants exterminated. 



New centres may be formed, and are, as frequently observed, 

 through individuals, carried accidentally by instinct, gusts of wind, &c ., 

 to other favourable spots of bush; but, again, the chances are much against 

 the preservation of the same ratio of species, especially where overstocking 

 is such a prevailing evil as here, and the tendencies in settled districts 

 are always towards extermination. 



This result would be rather beneficial to man than otherwise if 

 nature acted discriminatingly, which is not the case, extermination be- 

 falling the innocuous and the useful almost always in the first instance, 

 the others apparently receiving an impetus in the opposite direction, 

 completing the work of destruction, initiated by man unwittingly, in an 

 increasing ratio. 



Insects, as well as animals, being either herbaceous or predatory, 

 the former draw their sustenance from vegetation direct, while the 

 existence of the latter depends upon the first, limiting their increase 

 within narrow bounds, fluctuating little in a normal state of nature. The 

 great majority of predatory insects (ants, spiders, parasites, and pseudo- 

 parasites excepted) produce a much smaller number of ova than the 

 vegetable feeders, and are therefore more exposed to reduction in number 

 and final extermination by inimical eauses than their prey the vege- 

 table feeders. These, in their turn, are, in general, gifted with a 

 prodigious fecundity. 



Now, if one or more species of the predatory insects be extinguished, 

 or only greatly reduced in number, the check upon the herbaceous in- 

 sects, or upon some of them, is removed, and they at once avail them= 

 selves of the opportunity, and appear in augmented numbers, sometimes 

 inconceivably large, ending, after total destruction of their food-plant, by 



