116 Experimental and Statistical Studies upon Lepidoptera 
The comparison of the surviving pupae with an approximately equal number 
of dead pupae, and tlie comparison of the perfect survivors with the remainder of 
the group of survivors, has been based upon the following characters, numbering 
ten: first, two measures of the pupa as a whole, (1) the total length, the distance 
A — B in the diagram, and (2) the weight in milligrams; in the second place, 
a group of characters of the immovable anterior part of the pupa, which may for 
convenience be termed the " bust," and which extends back to the posterior ends 
of the wing-cases, at the level of the line between the fourth and fifth abdominal 
segments. The characters in question are (3) the length of the bust, the line 
A — C, (4) the width of the bust, the line D — E, (5) the dorso- ventral depth of the 
bust, the perpendicular line at the point F. From these measures were determined 
(6) the frontal proportions of the bust, as the ratio between the width and length, 
and (7) the sagittal proportions, as the ratio between the length and the depth of 
the bust. In the third place, certain measurements were made of a typical organ, 
the left antenna, namely (8) the length, the line K — /, and (9) the width, as the 
line / — K \ from these were determined (10) the proportions of the antenna. All 
the measurements are in mm. 
Of these characters two must be omitted in considering elimination of the first 
period, namely, length and weight, for after death evaporation and the consequent 
shrinkage of the free abdominal segments render these characters useless. While 
it is possible that alterations in the characters of the bust may follow death, thus 
invalidating any comparison between dead and living pupae, these altei-ations if 
indeed they occur, must in the nature of the case be very slight. We shall have 
H 
B 
Fig. 1. Diagram of the Saturnid Pupa. 
