44 MEMOIRS OF THE NATIONAL ACADEMY OF SCIENCES. 



3. The protlioracic segment not yet forming a Looil, the Iiead not retracted within it so readily 

 as in the hxst stages. 



4. The tubercles each bear only three three-forked ghindular setse. 



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



6. The body is pearly white, slightly purplish on the back. 



B. EVOLUTION OF ADAPTATIOXAL FEATl'RES. 



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

 beiug armed with numerous spines and some of them tinted with red. 



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



itECAPITULATION OF THE MORE SALIENT ONTOGENETIC FEATURES OF LITHACODIA FASCIOLA. 



A. CONGENITAL FEATURES. 



1. The larva is hatched without any tubercles. 



2. The glandular Lairs are of the same size and shape in the dorsal and 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. 



B. EVOLUTION OF ADAPTATIONAL FEATUBES. 



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



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



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

 or IV. 



4. In the last stage the minute spines disappear. 



VI.— GEOGRAPHICAL DISTRIBUTION OF THE AMERICAN NOTODONTID.€. 



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 equator to the i)oles. 



Mr. Wallace' states that the distribution of butterflies corresponds generally with that of 

 birds in showing a primary division of the earth into eastern and western rather than into 

 northern and southern lands. From his studies on the ilistribution of butterflies and " Sphingina" 

 (including, however, the ^-Egeriidse, Castniida?, Agaristidi^, Zygiienidie, Uraniidte), he concludes 

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



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

 striking manner wheu descending from the temperate zone of Mexico to Cordova, which is 

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

 States siiecies of this family have been derived from the tropical regions of Central aud 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 present will be therefore confined to the Notodontida;. 



It may, however, be well to bear in mind some general results which are quite obvious to one 

 who has paid even slight attention to the Bombyciue moths. 



While the Notodontidte appear to be both tropical and temperate forms, though it should be- 

 borne in mind that we know but little of the tropical forms, and few species are known from India 

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



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



