February, '16] HOWARD: HAWAIIAN INSECT INTRODUCTIONS 177 



Galesus and the Dirhinus, both pupa-parasites and received in the 

 greatest numbers, have not yet become established. They have been 

 put out in quantity but have not been recovered in the open. Whether 

 the character of the soil is the trouble, or whether they are alt destroyed 

 by the fire ant is a question. 



The Braconids were discouraging from the start. Opius perproximus 

 failed. Opius humilis and Diachasma tryoni were divided. Four 

 females of Diachasma and three females of Opius were liberated in 

 the district of Kona. Those retained in breeding cages were lost. 



Now comes the extraordinary thing. From the insignificant 

 number of seven females of the Diachasma and Opius liberated in 

 Kona, both species have become established! Both are larva-para- 

 sites, and were rediscovered by Mr. Giffard and Doctor Back. An 

 examination made by Back and Pemberton in the summer of 1914 

 indicates percentages of parasitism as high as 85 in larvce from coffee 

 berries grown in the Kona district, 97.8 per cent in larvse from coffee 

 berries at Lanihau and high percentages in other fruits at other 

 places. 



The Earlier Introductions 



The earlier introductions of parasites and beneficial insects against 

 injurious insects, made by Koebele before the outbreak of the sugar 

 cane leaf -hopper, have been rather fully considered in Mr. Swezey's 

 paper and elsewhere. Very many of them undoubtedly did excellent 

 work. In spite, however, of the large numbers of enemies of mealy- 

 bugs that were introdueed at that time, outbreaks are frequent though 

 not serious; and, although efficient parasites were introduced for leaf- 

 rollers and the latter are not now very injurious, outbreaks occasionally 

 occur. This, however, is quite to be expected, and in any considera- 

 tion of the value of imported parasites we must never expect extermina- 

 tion but a reduction to comparatively non-injurious numbers with an 

 occasional increase to some extent. 



In the case of none of these earh* introductions was there sufficient 

 study made of the intimate biology" of the species introduced, and in 

 fact the most careful study should be made now of the intimate life- 

 history of the recently introduced parasites, and especially of those 

 which are still coming in from Mr. Fullaway. Some of this work 

 I hope Mr. Timberlake will be able to do. 



Just why they have been able to accomplish so much is at first 

 glance rather hard to understand. As early as 1897 Mr. R. C. L. 

 Perkins, writing in Nature (Vol. 55, No. 1430, March 25, 1897), and 

 referring to the successes of the importations of many species by 

 Koebele for the purpose of destroying various crop pests, wrote as 

 follows : 



