58 PROCEEDINGS OF THE AMERICAN ACADEMY 



same plane with the embryo, just before exclusion, of the more highly 

 specialized forms of the group Attaciuae. The great size of the At- 

 tacinse, particularly Attacus atlas, appears to be a sign of recent 

 specialization, and the small size of Saturnia, aside from its other 

 features, suggests that it is a generalized form, not departing greatly 

 from the normal size of the members of the superfamily Bombyces. 



And here an interesting problem in zoogeography occurs. Are the 

 species of Saturnia (in the restricted sense) — three in Europe, and 

 two in the Southwest and Pacific Coast of North America, occurring 

 where the Attacinge do not exist at all, or only rarely — the relics of a 

 Saturnian fauna from which the group Attacina? has been eliminated 

 by geological extinction, as the sequoia, cypress, magnolia, and other 

 Tertiary plants have been rendered extinct in Europe, or may the 

 view be taken that the Attacinse have never had a foothold in Western 

 Eurasia and North America ? 



Should we use the characters drawn from the number and arrange- 

 ment of the tubercles of the larva in classifying the Saturniidee, we 

 might divide the family into two groups, as follows : — 



A. Six tubercles on the 8th abdominal segment ; the tubercles in 

 general over the body all of the same size. Generalized forms. 



Subfamily 1. Saturniince. 



B. Five tubercles on the 8th abdominal segment, the median one 

 double ; the tubercles in general more or less diflerentiated or special- 

 ized in size and color. Specialized forms. 



Subfamily 2. Attacince. 



An interesting series of parallelisms may be observed in comparing 

 the early and later stages of the larvae of this family. For example 

 while the late embryos of the Attacinae are perhaps paralleled by the 

 fully grown larva of Saturnia, the fully grown larva of the most or one 

 of the most generalized Attacinse, Platysamia, is on the same plane 

 of specialization as the larva of Callosamia in its third stage. 



The Life History of Platysamia cecropia (Linn.). 



From some eggs received from Mr. H. Meeske, of Brooklyn, N. Y., 

 the larvae hatched out at Providence during the night of June 14. 



Egg. — It is large, flattened, oval-cylindrical. Length 2.5, breadth 

 2 mm. The shell is dull chalky white, is seen under a triplet to be 

 pitted, but under a half-inch objective the pits are seen to be in close 

 irregular wavy parallel rows, the pits themselves showing a tendency 

 to be grouped into twos or threes. 



