OF WASHINGTON. 325 



by these gayly-colored insects. All are predaceous or parasitic, 

 and destroy annually thousands and thousands of destructive 

 insect pests. 



The economic value to us of the wasp and bee, however, is 

 probably much less in comparison with the benefits we derive 

 from innumerable parasitic ichneumon and chalcid flies. These 

 are numbered by "millions and are found everywhere. Most of 

 them, too, are so minute or microscopic in size as to escape our 

 notice, and it is only by the most careful observation in the field 

 and by breeding in the laboratory that we are able to obtain a 

 knowledge of their obscure mode of life. 



These belong principally to five families, the Proctotrypidae, 

 Cynipidae, Evanfidae, Chalcididae, Braconidae, and Ichneumonidae, 

 and all of them except the gall-making cynipids and a few phy 

 tophagous chalcidids, are genuine parasites, living in and de 

 stroying the eggs, larvae, pupae, and imagoes of the destructive 

 insect pests of the forest, field, and garden. 



The obscure habits of these parasitic Hymenoptera are now 

 being slowly worked out in various countries of the globe, and 

 more particularly in Europe and America. 



In recent years great interest in a study of these microscopic 

 species has been manifested, and it is gratifying to us to know 

 that in no country in the world is so much being done to make 

 known the habits and economic value of these insects as in our 

 own country. I allude particularly to the great work being 

 done in the U. S. Department of Agriculture, by its field agents, 

 and by our numerous Agricultural Experiment Stations. 



Our knowledge of the habits of certain groups and genera of 

 these insects is now sufficient to give us a good idea of those 

 species which are most important to the agriculturist and fruit 

 grower. 



For example, we have found out that whole groups of genera 

 and species are parasitic in the eggs of other insects and that 

 these are the most important. 



The species belonging to the family Mymaridae are parasitic 

 in the eggs of Hemiptera, Diptera, Neuroptera, &c. Certain 

 Proctotrypids belonging to the tribe Scelionini destroy the eggs 

 of destructive orthopterous insects, grasshoppers, katydids, 



