124 Annals Entomological Society of America [Vol. VII, 
Plate XXIII—First two layers of muscles of the first two segments of the 
abdomen of Malacosoma americana, the first layer on the right. 
In all the preceding dissections the caterpillar is represented as if opened on 
the dorsal line and spread out flat, so that the mid-dorsum is divided between 
the two edges and the midventral line lies in the middle. 
Plate XXIV—Ventral musclature of the posterior segments of Sphecodina 
abbotii. The left side is shown as seen from the inner side. 1, as seen when opened 
and spread out; 2, after removing the muscles hatched in Fig. 1; and 3, similarly 
after removing those hatched in Fig. 2. The principal nerves are.shown as wavy 
black lines; the segments are numbered and their boundaries indicated in Fig. 1 
by arrows. 
Plate XX V—Diagrams of segment. 
Fig. 1. An abdominal segment (left half) spread out and with the principal 
annulets and regions labelled, modified after Berlese. 
ACRO. acrotergite. a 
PRO. protergite. 
MESO. mesotergite. 
META. metatergite. 
The four sternites are similarly placed. 
sp. spiracle. 
ap. tergostern. tergosternal apodeme, pleurosternal suture, or subventral 
fold. 
ante. antecosta (ventral end). 
pre. precosta. 
inter- intercosta. 
pl. planta of proleg. 
g, w. Minor apodemes. 
w. ringlike folds, considered by Berlese to mark rudimentary segments of 
the leg. 
Fig. 2. A similar diagram of the metathorax, as developed, e. g. in Sphecodina. 
w. Wing-bud, marking the upper boundary of the pleurites. 
pleur. pleurite, its boundaries indicated by arrowheads. 
m. cx. membranous part of coxa. 
ch. ex. chitinized part of coxa. 
ACRO, PRO, MESO. and META,., as in Fig. 1. 
Fig. 3. A superposition diagram of the muscles of the metathorax as seen 
from within. Each muscle is represented by a double line, interrupted 
where it passes under another, and the insertions are shown as heavy 
black bars or dots. The diagram is meant to show the relative position, 
insertion and direction of action of the muscles, but not their size or 
form, and is supplementary to Pl. XIX. The rudimentary spiracle and 
trachea is indicated to the right of the letter 6. Middorsum at left 
edge, mid-venter at right. c and k, which cross far beyond the middle 
line, are only partly shown. 
Fig. 4. A similar diagram of a middle abdominal segment, serving as an 
index to Plates 4-6. Dorsally the precosta and intercosta are shown, 
laterally the antecosta, and ventrally the precosta, pleurosternal suture, 
apodeme ¢ (running to the left of the letter ¢) and the oval indicating 
the boundary of the proleg. The ganglion is dotted, and the anterior 
nerve indicated as a waved line. 
