INTRODUCTORY REMARKS 



The pai-asites considered in this Bulletin all belong to the 

 Dryinidae, a family of insects which, so far as is known, confine 

 their attacks to certain groups of the Homopterous Rhynchota, 

 popularly known as leaf-hoppers. The material which has been 

 studied is chiefly from two sources : (i) the species observed and 

 collected by Mr. Koebele and myself in Queensland from June 

 till the end of December, 1904, and (2) some of the species sent 

 to these islands from Ohio and California by Mr. Koebele in 

 1903; to which may be added two species peculiar to these isl- 

 ands. With regard to the parasites sent from Ohio and Cali- 

 fornia, those which I have described below by no means include 

 all the species sent by Mr. Koebele, and probably few or none of 

 the rarer ones are represented. This is due to the fact that un- 

 less a considerable number of individuals were sent, I was un- 

 willing to lose the chance of establishing a species in these isl- 

 ands by killing specimens for purposes of study. I now regret 

 this fact, as had I made a critical study of these insects at that 

 time, I should have found out what I now know, that many of 

 the parasites sent by Mr. Koebele would not have been the least 

 likely to accomplish the object for which they were sent, that is 

 to attack the sugar cane leaf-hopper, since their structure is in 

 certain respects quite different from that of those which attack 

 leaf-hoppers of that group. From want of this knowledge much 

 time and trouble were wasted in attempting the impossible ; while 

 several species sent, which were quite likely to attack the cane- 

 hopper and to become established, suffered accordingly for want 

 of attention, when this shouftl have been entirely centered on 

 them. The material for study that has passed through my 

 hands, dead or alive, has been very large. Mr. Koebele sent to 

 Honolulu from Ohio and California (but far the greater part 

 from the former State) some three thousand cocoons, which pro- 

 duced several genera and many species. During the time these 

 were being received, I bred many thousands of the Hawaiian 

 Rclithrodclphax for distribution in localities from wliioh it was 

 absent. In the six months spent in Australia, we reared a still 

 greater number of species. Indeed when one considers that 



