MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 53 



Routes of secular migration."— Passing from Soutli into Central Ainei'icii l)y the Isthmus of 

 Panama tho species o-radually peopled each coast, though nioi-e prevalent alony- the Gulf of Mexico; 

 thence passiiij^ along the tropical Ijclt of Texas. A few of the moiv iiardy forms, as those of 

 Anisota, Citheronia. and Eacles, became adapted to or originated in tlir valley of the Mi-ssissippi 

 and tiie .\tlantic coast region, two Anisota> finally reaching the region around the Bay of Fundy 

 and the St. Lawrence Valley as far down as Quelu'C. 



Perhaps as late an arrival in the Appalachian province as any of the group was Adelocephala 

 hi'serta. whose range in the United States is so fur as yet known restricted to the warmer parts of 

 Texas and to the valleys of the Mississippi antl Ohio, not perhaps having yet reached the Atlantic 

 coast or the region east of the Alleghanies. 



Although the Ceratocampida- is a more primitive group than the Saturniidie. the question 

 arises whether they did not pass from Neogala into Arctogiva long after the latter. That they 

 did is indicated by the wide distribution of the SaturniidiB in North America and in fact through- 

 out tropical and temperate Arctogsva. For example, in North America the species of Samia 

 nuist iiave occupied the continent, for the genus is represented throughout its width from the 

 Atlantic to the Pacific. The species may not have become ditierentiated until the present climatic 

 features of North America were established. This is indicated hy the fact that Samia cecropia 

 appears to be the ancestral species, which, as it spread west, gave off the form (.S. gloveri!) adapted 

 to the Rocky Mountain and Great Basin region, the boreal form, S. columhia, and finally the 

 Pacific coast form. .S. caHfornica. xhlloopluda hixeeta and perhaps A. hteoJor may not have 

 entered America north of Texas until after the glacial period had passed away. 



JVeogaa the ancestral home of the group. — From the foregoing facts it will be seen that the 

 original source of the Arctogwic forms was Neoga?a, and probably that the group originated in 

 the Brazilian sultregion. It is here that the most priniitive species of Adelocephala occur, as 

 also those of Citheronia, both of the genera toeing richest in species in the foi-est region of 

 tropical eastern South America. The genus Syssphinx (and Crinodes, if it be a member of this 

 family) is wholly confined to the Neogicic realm. 



Oeological date of the secular migration into Arctogsea. — Here we shall have to follow the 

 clew discovered by the vertebrate paleontologists. It is probable that tiie group was at first 

 confined to the South American continent, not passing northward into Central America until the 

 elevation of the Isthmus of Panama at the end of the Miocene Tertiary. This would indicate 

 that the Ceratocampid* and the family of Notodontidie, from which the former originated, 

 probably date back to the beginning at least of the Pliocene Tertiai'y. 



XV. THE FORE-TIBIAL SPUR OR EPIPHYSIS. 

 (PI. XXXVI, figs. 12-24.) 



This movable appendage arises from near the base and is articulated to the inside of the tibia 

 of the fore legs. It is the tibial epiphysis of Smith, the ^'schieneiiplatte'' of Dahl, ^^schieiten- 

 Mdttchen^^ of Kathariner, and the "spur of the fore tibia" of Rothschild and Jordan. It is well 

 developed in the Ceratocampina?. It has the same general shape and size as in the Sphingidse, 

 in which it universally occurs, Rothschild and Jordan* stating that it is "never absent." It is, 

 as stated by Speyer"^ and afterwards by Smith'' and later by Kathariner, present in the Papilion- 

 idse and Hesperidaj and "all Heterocera," except the Hepialidaj and, according to Rothschild 



« We propose the term "secular migration" for the slow migratory movement? of organisms extending through 

 one or more geological periods. Seasonal migrations may be applied to those annual migrations of animals 

 which take place in spring and autumn. 



<> Rothschild and Jordan, A Revision of the lepidopterous Family Sphingidse. Xovitates Zoologicse, IX, 

 Suppl. 1903. 



<^Isis. 184S, III, p. 101, figures. 



rf J. B. Smith, Bull. Brooklyn Ent. Club., VII, p. 69. Sept., 1884. 



