LEPIDOPTERA. 
357 
pupa is represented by Figure 436 and the cocoon by Figure 
437 . 
The Cecropia-moth occurs from the Atlantic coast to the 
Rocky Mountains. In the far West its place is taken by 
very closely allied forms, which are supposed to be distinct. 
In these the ground-color of the wings is usually a reddish 
or dusky brown. The form occurring in Utah and Arizona 
is Sarnia gloveri (S. glov'er-i); that found on the Pacific 
coast is Sarnia californica . 
The Ailanthus-worm, Philosamia cynthia (Phil-o-sa'mi-a 
cyn'thi-a), is an Asiatic species that has been introduced into 
this country. It has become a pest in the vicinity of New York, 
where it infests the Ailanthus shade-trees. The moth differs 
from all our native species of this family in having rows of 
tufts of white hairs on the abdomen. The cocoon resembles 
that of the Promethea-moth. 
Family Lacosomid^e (Lac-o-som'i-dae). 
The Sack-bearuig Frenulum-losers. 
This family so far as is now known includes only two 
species that are found in the United States, and both of 
these are rare; farther south several other species occur. 
They are our only native Frenulum-losers that retain a rudi¬ 
ment of the frenulum, but, as in the silk-worm, this frenulum 
is very small and the humeral angle is greatly expanded, so 
it is probable that the frenulum is of but little if any use 
(Fig. 438). It was the presence of this rudiment that first 
suggested to the writer that those families of the Lepidop- 
tera that we have termed Frenulum-losers were descended 
from frenulum-bearing ancestors. 
The Lacosomidae seem to be the sole survivors of a very 
distinct line of descent. In many respects they appear to 
be closely allied to the Saturniina, especially to the Bom- 
bycidae. But they differ markedly both in the structure and 
in the habits of the larvae; and, too, the wings of the adult, 
