Packard.] 
514 
[Feb. 19, 
In many Notodontidse the first abdominal segment bears a con- 
spicuous hump, sometimes forked, often ending in a seta. 
In the larval Ceratocampidse, either the prothoracic segment or 
the second and third thoracic segments bear high conspicuous horns 
and spines. They may be roughly classified as follows : 
Prothoracic segment. — With a large, subspherical tubercle on 
each side bearing numerous radiating hairs (Lasiocampidse of first 
stage), or pencils of hairs (Parorgyia) ; two antlers ( H . guttivitta ) 
Second thoracic segment. — Two high, slender spines. First stage 
of Anisota senatorial A. stigma and Dryocampa rubicunda. 
Third thoracic segment. — Two spinulose pappose flaps, Empre- 
tia stimulea. 
First, second and third thoracic segments . — Each with a pair of 
high spines, Cither onia regalis and Eacles imperialis. 
Second and third thoracic segments. — Each with a pair of long 
horns, Sphingicampa bicolor. 
First and third thoracic segments. — In stage I of the European 
Aglici tau (Poulton). 
First abdominal segment.— Movable tubercle in Schizura and 
Janassa. 
Eighth abdominal segment.— The caudal horn of Sesia and most 
Sphingidse, Pheosia and Endromis, Bombyx mori and other spe- 
cies, Sphingicampa, Eacles, Citheronia, and Aglia tau (stage I). 
So far as I am aware, no one has suggested why these horns and 
high tubercles and often pencils of hairs are restricted to these par- 
ticular segments. As a partial explanation of the reason, it may 
be stated that the presence of these high tubercles, etc., is corre- 
lated with the absence of abdominal legs on the segments bearing 
the former. It will also be noticed that in walking the apodous 
segments of the caterpillar are more elevated and prominent than 
those to which the legs are appended. They tend to bend or 
hump up, particularly the first and the eighth abdominal, the ninth 
segment being reduced to a minimum and the tenth simply repre- 
sented by the suranal and paranal plates, together with the last 
pair of legs. 
As is well known the loopers, or geometrid worms, while walk- 
ing, elevate or bend up the part of the body situated between the 
last thoracic and first pair of abdominal legs, which are appended 
to the seventh uromere. Now, in the larva of Nematocampa ftla- 
mentaria , which bears two pairs of remarkable filamental tubercles, 
