THE AXIMxVL LIFE OF THE GROrP. 381 



the ordinary observer, or those ])ersons whose occupations often bring them in 

 touch with things of nature. 



It is a singular fact that of the large number of species jx-culiar to the 

 islands only a few are noticeably destructive to agriculture or to ciillivaled 

 exotic plants. The worst enemies of the agriculturist have been introduced 

 from abroad and are frequently cosmopolitan j)ests. They usually come with 

 fa I'm produce, ornamental plants, earth and seeds. The result is that one is 

 liable to meet here in the islands all of the old enemies of tlie Imsbandmaii with 

 which one nuiy be familiar in his native country, and to the list may l)e added 

 several other forms equally destructive that were before uidviiown to the 

 observer. 



The number of destructive insects in the islands has led to the adoi)tion of 

 the i>oli('y of controlling them whenever possible by the introduction of their 

 natural enemies. This plan has been steadily pursued for almost a quarter 

 of a century, with the result that probably in no other country, particularly 

 when its size is considered, have so many benelicial insects been artificially 

 established. 



Control by Natural Enemies. 



As the natural enemies of most of the insects are parasites, which as very 

 minute insects, usually attack and feed in one way or another upon the host 

 species wdiich itself is often microscoj^ic in size, this warfare is not a very 

 conspicuous one, nor one liable to attract very much attention. However, in 

 the struggle l)eing continually waged to keep the enemies of agriculture in 

 check in the islands, these often unseen and unknown insect friends are always 

 active and have already saved millions of dollars to Hawaii. 



The Stgar-Cane Leaf-Hopper. 



Perhaps no more remarkable example of the effectiveness of this method 

 of control can be found than that of the introduction of the leaf-hopper c^^^^ 

 parasites. The cane leaf-hopper had been known to plantation managei-s and 

 expert entomologists in the islands for a number of years, but in the early 

 spring of 1908 it appeared so generally throughout th(^ cane fields and in such 

 numbers as to prevent the growth of the cane. It was found to be a typical 

 member of the leaf-hoi)per family { Asl)-aci(}((') . and ju-ovimI to l)e a i-eccMit in- 

 troducti(»n, ])i-o])ably ])i-onght with seed caiu' fi'om (Queensland. Australia. 

 Owing to its small si/.e and inconspicuous color and habits, its spi'ead was un- 

 noticed until it could be found almost wherever cane was grown. 



The sugar-cane leaf-hopper- Hies readily and is attracted long distances 

 by liulit : so besides ti'aveling with the cane, it llew to new lields an 1 from 

 one plantation to another. 



A peculiai' smut that developed on the lowei' leaves of cane attacked by 

 the leaf-hopper was found to l;i-o\v on the ■'honey dew,'" a ti'ansparent sticky 



- Perkinsii'lhi xiirrhii riciihi. 



