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hope of exterminating the weevil, yet by planting the cotton early and 

 getting the varieties that mature early, they can obtain much better results 

 than in the late crops ; while with good cultivation, planting the rows wide 

 Apart, and the ploughing up of cotton fields and burning up of all cotton 

 stalks after the crops are harvested, the pest may be very greatly reduced, 

 and in clean cultivation immense numbers of the adult weevils that hibernate 

 through the winter would be destroyed. 



Another example : The Colorado Potato Beetle (Leptinotarsa decemlineata) 

 is a native of the Rocky Mountains, where it was, until about 1855, a 

 common beetle on several weeds belonging to the same natural order of 

 plants as the cultivated potato. About this date it became acquainted 

 with the latter more succulent plant. It multiplied in such numbers that it 

 spread from one end of the States to the other ; and Saunders, in " Insects 

 injurious to Staple Crops, 1902," says : " It is safe to assert that this pest may 

 to-day be found almost wherever the potato is grown in the United States 

 or southern Canada." 



In a very similar manner there appeared what is a very serious pest to 

 the citrus tree in the northern rivers district of New South Wales. 

 When the virgin forest was cleared off the land near Lismore, among 

 other trees growing in the scrub was a "wild finger lemon," one of the 

 few representatives of the citrus family indigenous to Australia. In this 

 a large longicorn beetle (Uracanthus cryptophaga) lived, the larva boring 

 holes all through the branches. Orchards planted on this cleared forest land 

 were attacked by a borer, which on examination proved to be the larva of 

 this wild lemon longicorn. 



The question is often asked, " Why do the grasshopper, locust, and cut- worm 

 plagues only occur every few years in a very acute state, though we always 

 have a few about T There are several reasons : First, climatic conditions, 

 such as a very dry or very wet season, check or increase the development of 

 the eggs ; next, we find that many of these recurrent plagues gradually increase 

 in intensity for several years until they have reached their limit ; then para- 

 sites increase in proportion, or fungus diseases, which are spread by the 

 immense number of insects contaminating the feeding grounds, kill them off 

 in millions. 



To an observant man it is quite apparent that while great numbers of 

 insects are preyed upon by other insects, Nature makes provision for this in 

 the immense reproductive powers of all insects that are liable to excessive 

 parasitism. The fecundity, apparently useless and wasteful, of some of our 

 great wood-boring moths (Zeuzera, Leto, &c.) in producing the thousands of 

 egos contained in their ovaries scattered over the bark, and from which later 

 very few larvae ever enter the trunk would be appalling but for the thought 

 that they are the probable food supply of some smaller forms. 



Australia stands alone in its isolated fauna and flora, so that there are 

 certainly not so many native trees in our forests closely allied to cultivated 

 plants as there are in most parts of the world. If we had not introduced 

 our orchard pests, we had very few in our orchards from native trees. 



Before we can go into the question of pests and parasites, it is only reason- 

 able that we should first know something about the habits and life histories 

 of the insects of both pests and parasites before we attempt to alter the 

 balance of nature, and set " bug to fight bug " a popular saying in the 

 United States. Yet we are often told, in the newspapers and elsewhere, that 

 it is not necessary to be an entomologist to undertake the collection and 

 introduction of foreign parasites ; that it is a disadvantage, in fact, for one 

 may be too good an entomologist to be a practical man. The danger of a 



