OF WASHINGTON. 431 



region to another, and from one country to another, of such as 

 are known to do good in one section but do not yet occur in 

 others in which the host pest abounds. Its importance is so self- 

 evident that further consideration is unnecessary before the mem 

 bers of this Society. 



Thus* the parasites of my first category are not directly or 

 necessarily fatal to their host and are chiefly harmful through 

 indirect consequences which they induce ; while those of my 

 second category, or the truly entomophagous forms, are for the 

 most part fatal to their hosts, and since these are, in the majority 

 of cases, plant feeders indirectly quite beneficial to the agricul 

 turist. 



CONCLUSION. 



It is evident that within the brief compass of this annual ad 

 dress full justice cannot be done to the different interesting phases 

 of this subject of insect parasitism. With but slight extension the 

 term would include a host of other insects of different orders, as, 

 for instance, those which produce galls on plant tissues, and 

 the true fig insects. These I have omitted from consideration. 

 I have also been obliged to deal very largely in broad, general 

 statements and to avoid too much detail. An interesting chapter 

 might be devoted to the habits of each of the genera in most of 

 the parasitic families. I have also omitted all consideration of 

 the modification of the cocoon due to the parasitic habit, as 

 well as all consideration of another interesting phase of the 

 subject, viz., the psychic effect upon the parasitized animals. 

 The imperfect review, however, which I have given of actual 

 parasitism, shows that this condition is most pronounced and 

 most characterized in the higher forms of insects, or those under 

 going complete metamorphoses. This fact, taken in connection 

 with the many others which I have considered, or which might 

 be cited, goes to show that the parasitic forms and the parasitic 

 habit have appeared late in the history of insect evolution on the 

 globe, thus further confirming their derivative origin from earlier 

 forms. 



