OF WASHINGTON, VOLUME XII, 1910. 89 



If, now, we look at the distribution of the orb-weaving spi- 

 ders (Epeiridaa) in our country, we note at once that there is 

 little difference east aud west, but much greater difference 

 north aud south. Many of the northern forms are European 

 species and range from Maine to Vancouver. A peculiarity 

 of these northern species is trnt they extend farther south in 

 California than in the Eastern States. Similarly the genera 

 like Acrosoina, that extend up from the South into all parts of 

 the southern United States, range farther northward in the 

 Eastern States than on the Pacific Slope. With these south- 

 ern spiders we can trace the extension of southern faunas up 

 into valleys that open to the South. So if we map the distri- 

 bution of our Epeiridse we must pay little attention to eastern 

 and western areas, but to northern and southern; to the ex- 

 tension of northern forms southward along -mountains, and 

 the extension of southern forms northward along valleys and 

 coastal plains. There is nothing in this family to show that 

 the western forms are more European than the eastern ones. 



The small neuropterous family Mantispidae is of southern 

 origin, and extends in our country northward along valleys 

 and plains, in the East into Massachusetts, and in the central 

 plain into Canada. 



If we consider the distribution of the Phalangida in the 

 United States, we must lay stress on the difference between 

 eastern aud western forms, and that the western is more 

 European. The families Nemastomatidse and Trogulidse, 

 fairly common in the West, are almost absent in the East, and 

 then only in the Northeastern States. In the Phalangida we 

 notice also this northern fauna extending across the country, 

 farther southward in the West than in the East; but in this 

 case there are few species that extend across the country, but 

 the genera have such an extension. Although there are vari- 

 ous elements in the West that show relation to Europe, yet 

 the largest genus in the family Liobunum is more abundant 

 in Europe and the Eastern States than in the West. In the 

 Phalangida we must also call attention to the forms, like Cy- 

 norta, that have spread northward from Mexico and the West 

 Indies. This genus has different species in the East than in 

 West, and in the East ranges farther northward. So in the 

 Phalangida we get a combination of the distribution seen in 

 the other groups considered; the relation of the Californian to 

 the European, the genera that spread up from the South, and 

 the genera that extend across the North. But all through 

 runs the difference between the East and the West. 



