THE ANIMAL LIFPZ OF THE GROUP. 381 



the ordinary observer, or tliose persons whose occupations often bring them in 

 touch with things of nature. 



It is a singular fact that of the large number of species peculiar to the 

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

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

 from abroad and are frequently cosmopolitan pests. They usually come with 

 farm 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 the husbandman with 

 which one may be familiar in his native country, and to the list may be added 

 several other forms equally destructive that were before unknown to the 

 observer. 



The number of destructive insects in the islands has led to the adoption of 

 the policy 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 countiy, particularly 

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

 established. 



Control by Natural Enemies. 



As the natural enemies of most of the insects ai"e parasites, which as very 

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

 species which itself is often microscopic in size, this warfare is not a very 

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

 the struggle being 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 Sitgar-Cane Leak-Hopper. 



Perhaps no more remarkalile example of tlie effectiveness of this method 

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

 parasites. The eane leaf-hopper had been known to plantation managers and 

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

 spring of 1903 it appeared so generally throughout the 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-hopper family {Asiracidce), and proved to be a recent in- 

 troduction, probably brought with seed cane from Queensland, Australia. 

 Owing to its small size and inconspicuous color and habits, its spread 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 light: so besides traveling with the cane, it flew to new fields and from 

 one plantation to another. 



A peculiar smut that developed on the lower leaves of cane attacked by 

 the leaf-hopper was found to grow on the "honey dew," a transparent sticky 



= Perkinsiella snerhnriridn. 



