44 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



3. The protlioracic segment not yet forming a liood, the head not retraeted withiu it so readily 

 as in the last stages. 



4. The tubereles each bear only three three-forked glandular setae. 



5. The segments are more distinct than in the later stages. 



6. The body is pearly white, slightly inuplish on the bai^k. 



It. EVOHTION UF ADAI'TATIONAL KEATIRKS. 



1. The body in Stage IT assumes nearly the form and colors of the last stage, the tubercles 

 being armed with numerous spines aud some of them tinted with led. 



2. In Stage III the colors and appearance of the full-fed larva are assumed. 



RECAPITULATION OF THE MORE SALIENT ONTOOENETIC FEATURES OF LITHACODIA FASCIOLA. 



A. COX<lEXnAL FEATURES. 



1. The larva is hatched without any tubercles. 



2. The ghiudular hairs are of the same size and shape in the dorsal aud subdorsal rows, being 

 short, with a tine at the middle and forked at the truncated end. 



3. The body is more cylindrical than in the last stages and not skiff-like, and the segments are 

 distinct and simple. 



i. The body is at first colorless. 



n. EVOLITIOX OF ADAPTATIONAL FEATCRES. 



1. The body becomes skiff'-like when 5.5 mm. in length. 



2. The color is pea green, like that of the leaf it feeds on, with straw- yellowish marks and spots. 



3. The skin becomes rough and granulated aud the plateau distinctly marked in Stage III 

 or IV. 



i. In the last stage the minute spines disappear. 



VI.— GEOGRAPHICAL DISTRIBUTION OF THE AMERICAN NOTODONTlD.i. 



MAPS i-x. 



The Lepidoptera are, as regards the higher groups, from the Bombyces to the butterflies, very 

 largely tropical, the number of species diminishing as we pass from the e<piator to the poles. 



:\Ir. Wallace ' states that the distribution of butterflies corresponds generally with that of 

 birds in showing a i)rimary division of the earth mto eastern and western rather than into 

 northern and southern lands. From his studies on the ilistribntion of butterflies and " Sphingiua" 

 (including, however, the .Egeriidie, Castiiiida", Agaristida', Zyga-nidie, Uraniidw), he concludes 

 that "the neotropical region is by far the richest and most jjcculiar." 



The Zyga-nidiP or day-flying moths are usually restricted to the Tropics, as we have seen in a 

 striking manner when descending from the temperate zone of Mexi(!0 to Cordova, which is 

 situated in the tropical zone (tierra calientc), and it is easy to recognize the fact that our United. 

 States species of this family have been derived from the tropical regions of Central and South 

 America and the Antilles. 



It would be premature for us to enter into even a provisional account of the distribution 

 of the Bombyces as a whole until we have completed our survey of the members of the entire 

 superfamily, and our remarks at iiresent will be therefore confined to the Notodontidie. 



It may, however, b(^ well to bear in mind .some general results which are quite obvious to one 

 who has paid even slight attention t(j the Hombycine moths. 



While the Notodontidie ai)pear to be both tropical and temperate forms, though it should be 

 borne in mind that we know but little of the tropica! forms, and few si)ecies are known from India, 

 or southern Asia in general, certain other families are largely tropical. 



' The Geographical Distribution of Animals, 1876, ii, p. 483. 



