252 MEMOIRS NATIONAL ACADEMY OF SCIENCES. vol. xii, 



In Rothschildia, as shown by blown examples of Rothschildia orizaba received from Mexico, 

 the tubercles are more rudimentary; they are low, short, fleshy, and are crowned with 5-7 

 small sharp spinules, while those of Attacus atlas are long, finger-shaped and unarmed with 

 any spinules. The median tubercle on the eighth abdominal segment is very small, incon- 

 spicuous, and but slightly larger than the other dorsal tubercles of the abdominal segments. 

 The dorsal tubercles on the meso- and metathoracic segments are scarcely larger, if any, than 

 those in the abdominal segments. 



Burmeister has figured the larva? of Rothschildia hesperus, ethra, aurota, betis, and spec- 

 ulifer. In all except R. betis they agree well with the larvae of R. orizaba; the thoracic, dorsal 

 tubercles being no larger than the abdominal ones, this species approaching nearest to R. au- 

 rota. In R. betis, however, no traces of tubercles are given, and in the text it is stated that 

 the larva? has no spines; the larva? is blackish, banded transversely with deep pink-red. The 

 larva?, then, of tho American species hitherto referred to Attacus appear to present excellent 

 distinctive characters. 



Judging by the larva?, whose tubercles are more like those of Samia, Rothschildia is the 

 more primitive type, and Attacus the more specialized. Attacus is in venation and the shape 

 of the wings closely allied to Philosamia (P. cynthia); its larva is more specialized than that of 

 Philosamia; but the latter has begun to be specialized in the reduction of the dorsal tubercles 

 of the prothoracic segment, which are short, rounded, and unarmed. 



Attacus is confined to the oriental region, while the older more primitive genus Philosamia 

 is represented in equatorial Africa as well as tho East Indies; it is probable that the Ethiopian 

 realm was the original home of these two genera, unless Attacus separated after migration into 

 th,e East Indies, India, and the East Indian Archipelago. 



ROTHSCHILDIA ORIZABA (Westwood). 

 Plate IV, figs. 1-3; VI; XLV, fig. 5; LXIV, fig. 2. 

 Attacus orizaba Westwood [Proc. Zool. Soc. Lond., 1853, p. 158, PI. 32, fig. 2]. 



Imago. — Four <? , five 9 . Of the usual fawn-brown. Thorax with a white band. In 

 the male the fore wings more falcate than in o* R. hesperus. The clear discal spot is triangular, 

 narrower on the fore than on the hind wings, but much alike on both wings, the outer apex of 

 the spot rounded, and either piercing the outer white line (extradiscal) or not quite extending 

 to it; the base of the discal spot either slightly concave or wavy. The extradiscal line is straight, 

 much more so than usual, more so than in R. jacobsese or hesperus, being either straight or slightly 

 waved or undulating from the apex [of] the clear discal area to the costa, or (one 9 ) straight, 

 not waved; behind, from this point to the inner edge of the wing, the line consists of two large 

 scallops, one in the first and one in the second median cell. The white line or band is edged 

 with yellowish brown; beyond is a broad diffuse lilac band, then becoming fawn color, this 

 shade bounded by the submarginal line which is scalloped from the apex to the first median 

 vein, and thence to the inner angle of the wing it is straight. The black spot in the second 

 apical cell is large and distinct, roundish; beyond is a brown figure 8 in one 9 (fresh and well 

 preserved); each part of the 8 is centered by a conspicuous dark brown spot, the two spots 

 being connected. No dark spot between this and the costa (as there is in R. jacobsese). 



Hind wings rather prolonged; the clear discal space distinctly triangular, not oval as in 

 R. jacobese and hesperus. The outer line consisting of six rounded, not angular scallops. The 

 spots on the marginal line are large and distinct. 



Expanse of fore wings, c? 132 mm.; 9 125-150 mm. 

 Length of fore wing, <? 68 mm.; 9 65-70 mm. 



One of my 9 s was compared with specimens so named in the British Museum. 



This is the commonest Mexican species. It differs from R. hesperus and jacobese in the outer 

 line of the fore wings being nearly straight and in the discal area being regularly triangular, not 

 rounded. In R. hesperus there are no subapical black spots at all. In R. jacobese the subapical 

 spot is triangular, and forms one of a series of several besides an apical black spot. In both 



