277 



culars sent out to call the next auimal meetiug" a cordial invitation 

 should be extended to any not members to be present and take part in 

 the meetings. 



Mr. Howard then read the following i)aper : 



THE HOST RELATIONS OF PARASITIC HYMENOPTERA. 



Bj' L. O. Howard. 



So many instances of the importance of the Hymenopterous parasites 

 of injurious insects are on record that there is no necessity of dwell- 

 ing upon it before a meeting of working entomologists. 



They are of greatly more importance to us than Dipterous parasites 

 not only on account of their vastly superior numbers, but in the ex- 

 tremely important j)oint of rapid breeding. Had Lestophonus, the 

 Australian Dipterous parasite of Icerya purchasi, which Professor Riley 

 sent Mr. Koebele to Australia to bring over alive, been a Hymenopter- 

 ous parasite like Euplectrus, for example, which Schwarz has shown 

 may occupy in the Southern States in summer the almost incredibly 

 short time of 8 days for a single generation, there would have been no 

 necessity for the now famous Vedalia cardinaUs, as even this rapid 

 breeder occupies 30 days in its life round, even under the most favorable 

 circumstances. 



With this advantage over Dipterous parasites, as well as over preda- 

 ceous insects, they have still another over the latter class of bene- 

 ficial insects, in that they are never cannibals, a habit which is often a 

 serious drawback to the otherwise fair characters of many predaceous 

 species. 



The importance of their work admitted, the importance of their study 

 follows as a necessary corollary, and perhaps the most important feature 

 of the results of such study is the attainment of that knowledge which 

 will enable us to recognize the limitations of each parasitic species ; 

 given a certain parasite, to know upon what it is liable to prey, or, 

 given a certain injurious insect, to know what parasites will probably 

 attack it. More precise knowledge will be gained when our rearings 

 will enable us to bring forth an accessible volume in which we may see 

 at a glance just what parasites have been reared from a certain injuri- 

 ous species, just what species have been reared from congeneric forms, 

 and, by a converse arrangement, just what hosts a certain parasite pos- 

 sesses. Grouping such facts will enable the most important generali- 

 zations and systematic classification will undoubtedly be aftected. 



Our ijublished knowledge in these directions is so far slight in this 

 •country, nor have the isolated records and shorter lists been brought 

 together in Europe. Some 4 years ago I began, as a basis for general- 

 ization as to the habits of restricted groups, the lumping of the Euro- 

 pean lists by means of a card catalogue. The task proved a much 

 greater one than I anticipated, and later Dr. Riley kindly afibrded me 



