MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 45 



Upon the whole, the Ceratocampidm are tropical, many more species occurring in Brazil and 

 Central America than in North America, and this may be said of the family Hemileucida'. 



The family iSaturniida- is a tro[)ical group, only a single genus occurring in Europe, while in 

 North America north of Mexico there are six. In tropical America, Africa, and southeastern 

 Asia, including Chiua, the species and genera are far more numerous and form a characteristic 

 feature of tlie fauna. 



Another fiimily richly developed in the tropics of South America, Africa, and Asia is the 

 extensive family of Lasiocampidn; many of them rivaling in size the colossal Attaci, and judging 

 from a collection of Central African caterpillars of this group in the museum of Brown University, 

 collected on the Upper Congo, their armature of spines is tlie most formidable of any of the 

 Bombyces. And here it may be observed that the most spiny forms appear to be tropical, and 

 this tends to prove that originally nearly all our spiny caterpillars appeared in warm regions, 

 while the densely hairy forms, like Arctian larvif, predominate in cool temperate regions. 



The I'sychhlcv, though so richly developed in Europe, appear on the whole to be widely 

 distributed over the tropical regions, including Australia. 



The group of CochUopodida' or slug caterpillars is richly developed in Central and South 

 America, as well as in India, but is entirely wanting in western North America, while in Europe 

 there are only two species, this paucity or absence of species being probably due to geological 

 extinction iu the western«portious of the Old and New Worlds. 



The small family of Meyalopyyidcc (Lagoida^) is confined to the New World. One genus ( Lagoa) 

 occurs iu the eastern United States, but the species are most, numerous in the forest regions of 

 eastern South America. 



The family LipaHdw appears on the whole to exist in greater force in the Tropics of America 

 and Asia than in the temperate regions to the northward. 



On the other hand, the extensive group of Arctiidw and Litlwsiidw predominate in the tem- 

 perate regions, and its species, in rare cases — a few of Arctia — extend to the Polar Regions, only 

 one other genus, Laria, a Liparid, sharing the regions of the Arctic Circle, a species of each genus, 

 Arctia and Laria, also being Alpine in Europe and North America. 



We will proceed to analyze the Notodontian fauna of North America. 



The animals of our American continent south of the Polar Region may roughly be divided 

 into three grand assemblages, i. e., (1) those inhabiting the northern moist and forest-clad regions; 

 (2) those inhabiting the elevated, dry plateau region of the Cordillera mountain ranges, extending 

 southward over the Mexican plateau, and which may be called the Plateau Piovince (it is Allen's 

 Arid Province); (3) those inhabiting the tropical portions of southern Florida and the low tropical 

 shores of southern Texas and of Central America. 



In our essay on the geographical distribution of the Geometrid moths,' published in 1870, 

 we called attention to the elements from which our present insect fauna has Leeii formed, and 

 claimed that the tropical elements iu our fauna originally migrated from Central America by 

 three avenues, i. e., the Pacific Coast, the central plateau of the Cordilleras, and the Atlantic 

 Coast, and we have always been of the. opinion that the Mexican fauna had strongly influenced 

 the Pacilic Coast fauna, as well as the fauna of New Mexico, Utah, and Nevada. 



As to the Arid province, or Plateau province as it might also be designated, it may be observed 

 that within the limits of the United States it comprises the Central province of Agassiz, together 

 with the Pacific Coast or California province, and to which Dr. Allen gives the name of Campes- 

 trian subprovince. The southern equivalent of the Campestrian is the Mexican subjjrovince. We 

 very much prefer the word Mexican to the term "Sonoran" of Dr. Merriam.'' Originally the term 

 "Sonoran" was applied by Cope to a restricted portion of northwestern Mexico known politically 

 as Sonora. 



But Dr. Merriam has, somewhat unwarrantably it seems to us, extended the term "Sonoran" 

 to include not only the elevated portions of Mexico, but also almost the whole of the United States 



'A nionograpli of the Geometrid moths or Phala'nicla' of the I'uited States. Report IJ. S. Geological Survey, 

 F. V. Hayilen, geologist iu charge, Vol. X, 187(>. 



"The Geograjihlc Distiiliutiou of Life in North America, with special reference to the Mammalia. Proc. 

 Biological Society of Washington, vii, pp. 1-64, April, 1892. With a map. 



