128 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
of iv out of line up behind the spiracle and the development of a 
chitinous leg shield on the outside of the abdominal legs in the place 
of tubercle vii. Rarely (Notodontidae) the tubercle bases of certain 
setae may be prolonged into chitinous processes, single or, more 
rarely, branched, bearing the seta at the apex, as is so frequent among 
the Saturnina (Saturniides). In the highest forms the reduplication 
of the setae and conversion of the tubercles into warts occurs. On 
the abdominal segments each tubercle forms a wart except vii and 
viii; but even these form small warts on the apodal segments. Where 
the legs are present, vii has been already transformed into the leg- 
shield and the position of viii, on the inner side of the leg base, 
precludes the development of a wart. On the meso- and meta-thoracic 
segments a doubling of the tubercles takes place in wart formation. 
It appears from recent observations that in this process ia and ib 
united form the first wart, iia the second, iib the third, iii the fourth 
(iib and iii often absent), iv and v together the stigmatal wart, and 
vi the subventral one. The process is thus essentially different 
from the wart formation of the Microlepidoptera (Tineides) and 
Saturniides. On the prothoracic segment, the group of three pri¬ 
mary stigmatal setae and the group of two subventral setae form 
each a large wart. Of the six on the cervical shield, the pair on the 
lateral edge form a wart which tends to become detached from the 
shield and is often placed above the spiracle. The two on the 
anterior edge of the shield form a pair of small warts or are fused 
into a long wart or become merely an area for the development of 
long hairs overhanging the head, while the two setae near the pos¬ 
terior edge of the shield are represented by an irregular group of 
hairs or are obsolete. 
The ultimate evolution consists in the development of secondary 
hairs and the final degeneration of the warts to give place to this 
secondary coating. Rarely secondary hair formation may precede to 
a certain extent the appearance of warts or be accompanied by a 
partial development of these structures. 
As stated above, abdominal tubercles iv and v are remote and out 
of line, iv being dorsad to v. The only exceptions to this are in 
certain Thyatiridae, where the development of a few definite sec¬ 
ondary setae seems to have counteracted the dorsad motion of iv, 
and in the Eupterotidae, where warts iv and v are degenerate and 
have come to assume a generalized position, probably secondarily. 
Rarely, in the highest forms, wart iv may disappear by abortion 
