OF WASHINGTON. 201 



species and favor the development of local races and distinct 

 species. While, in some instances, the barriers are plainly 

 indicated by intervening stretches of the ocean, it is not easy to 

 point out the barriers on the continents, viz. , those which pro 

 duce the difference between the faunas of eastern and western 

 boreal American or between those of eastern and western 

 Siberia. 



Mr. Fernow remarked that animals are dependent on plant 

 life, and, as the latter is much influenced by climate, the local 

 faunas noted probably resulted from climatic conditions, which 

 would vary considerably within prescribed districts, as, for 

 instance, on the east or west coast of continents. 



Dr. Gill said that his attention had been forcibly drawn to 

 similar cases of extremely local distribution in Arctic species in 

 other classes of animal life. He mentioned in fishes a distinct 

 order and family, the Delidse, which have a very restricted 

 habitat, being confined to Lake Baikal, Siberia, and are not 

 known to occur elsewhere, and other similar cases. 



Mr. Marlatt presented the following communication : 



A STUDY OF THE OVIPOSITOR IN HYMENOPTERA. 



BY C. L. MARLATT. 



A study of the peculiar and, in a measure, abnormally de 

 veloped ovipositor of Metopius rileyi together with an examina 

 tion of the nature of its attachment to the terminal segments 

 of the abdomen led to some interesting results already recorded 

 in this volume of the Proceedings * and induced the writer to 

 make a series of dissections of the terminal segments and ovi 

 positor of other Ichneumonids and representative species of 

 other families of Hymenoptera. A brief summary of the out 

 come of this work is given in this communication. 



The older writers seem not to have very carefully studied 

 the ovipositor in this order of insects, with the exception of 

 Westwood, who gives a measurably accurate description and 

 figure of this organ in Pimpla instigator, \ which he says will 

 be found to agree with Uroceridse and Cynips. Of other 

 writers, he says that Reaumur, De Geer, Curtis, Latreille, 

 Gravenhorst amd Burmeister, who have figured and described 

 this instrument, have failed to trace its true structure. 



* Notes on the genus Metopius^ etc., pp. 101-105. 



t An Introd. to the Mod. Class of Ins., etc. Vol. ii, p. 139. 



