MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 53 



Routes of secular inigration." — Passing from South into Central America by the Isthmus of 

 Panama the species graduall}' peopled each coast, though more prevalent along the Gulf of Mexico: 

 thence passing along the tropical belt of Texas. A few of the more hard}- forms, as those of 

 Aiiisota. Citheronia. and Eacle^ became adapted to or originated in the valley of the ^Mississippi 

 and the Atlantic coast region, two Anisota? finally reaching the region around the Bay of Fund_y 

 and the St. Lawrence Valley as far down as Quebec. 



Perhaps as late an arrival in the Appalachian province as uny of the group was Ariel ocejihala 

 hisecfa, whose range in the United States is so far as yet known restricted to the warmer parts of 

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

 coast or the region east of the Alleghanies. 



Although the Ceratocampidw is a more primitive group than the Saturniida\ the question 

 arises whether they did not pass from Neogsea into Arctoga?a long after the latter. That they 

 did is indicated by the wide distribution of the Saturniidw in North Au>erica and in fact through- 

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

 must have occupied the continent, for the genus is represented throughout its width fi-om the 

 Atlantic to the Pacitic. The species may not have become differentiated until the present climatic 

 features of North Aiuerica were established. This is indicated by the fact that Samia cecropla 

 appears to 1)e the ancestral species, which, as it spread west, gave off' the form (.V. glover!!) adapted 

 to the Rocky Mountain and Great Basin region, the boreal form, *S'. Columbia, and finally the 

 Pacific coast form, .V. caUfornica. Adelocephala hisecfa and perhaps A. hicolm- may not have 

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



JVeogn'a the ancestral home of the group. — From the foregoing facts it will be seen that the 

 original source of the Arctogteic forms was Neoga;a. and probably that the group originated in 

 the Brazilian subregion. It is here that the most primitive species of Adelocephala occur, as 

 also those of Citheronia, both of the genera being richest in species in the forest region of 

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

 famil}-) is wholly confined to the Neogteic realm. 



Geological date of the secular migration into Arctogxa. — Here we shall have to follow the 

 clew discovered by the vertebrate paleontologists. It is proliable that the grouj) 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 Cei-atocampidie and the family of Notodontidiv, from which the former originated, 

 probably date l)ack to the beginning at least of the Miocene Tertiary. 



XV. THE FORE-TIBIAL SPUR OR EPIPHYSIS. 



il'l. XXXVI, ti;;^. lL>-24. I 



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 "schienenplatte" of Dahl, ^•^•■hicnm- 

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

 developed in the Ceratocampinse. It has the same general shape and size as in the Sphingidie, 

 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- 

 ida? and Hesperida; and "all Heterocera," except the Hepialida^ and, according to Rothschild 



a We propose the term "secular migration" for tlie slow migratory movements of organisms extending throiigli 

 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 tlic lejiidopterous Kiimilv Sphingida'. Novitates Zoologic;c IX 

 Suppl. 1903. 



"Isis. 184.3, III, p. 161, figures. 



rf J. B. Smith, Bull. Brooklyn Ent. Club., VII. y,. 09. Sept., 1884. 



