The Life-History and Anatomy of Butterflies 
costal, known as the subcostal, and the other preceding the sub¬ 
median, known as the median vein. The branches of these com¬ 
pound veins are known as nervules. The median vein always 
has three nervules. The nervules of the subcostal veins branch 
upwardly and outwardly toward the costal margin and the apex 
of the fore wing. There are always from four to five subcostal 
nervules. In the hind wing the subcostal is simple. The median 
vein in the hind wing has three nervules as in the fore wing. Be¬ 
tween the subcostal and the median veins, toward the base in both 
wings, is inclosed the cell, which may be wholly or partially open 
at its outer extremity, or closed. The veinlets which close the cell 
at its outward extremity are known 
as the discocellular veins, of which 
there are normally three. From the 
point of union of these discocellular 
veins go forth the radial veins known 
respectively as the upper and lower 
radials, though the upper radial in 
many genera is emitted from the 
lower margin of the subcostal. 
An understanding of these terms 
is, however, more readily derived 
from a study of the figure in which 
the names of these parts are indi¬ 
cated (Fig. 40). 
Butterflies generally hold their 
wings erect when they are at rest, Fig. 40.—Wing of Anosia pi ex- 
with their two upper surfaces in ^ 
proximity, the under surfaces alone veins; s C ,subcostal vein • 5 c% ,etc. 
displaying their colors to the eye. 
Only in a few genera of the larger 
butterflies, and these tropical species, 
with which this book does not deal, 
is there an exception to this rule, 
save in the case of the Hesperiidce , or “skippers,” in which very 
frequently, while the anterior wings are folded together, the 
posterior wings lie in a horizontal position. 
Internal Organs .—Thus far we have considered only the ex¬ 
ternal organs of the butterfly. The internal organs have been 
made the subject of close study and research by many writers, 
21 
subcostal nervules; UR, upper ra¬ 
dial ; LR, lower radial; M, median 
veins; Mi, M2 , M3, median ner¬ 
vules ; SM, submedian veins; I, in ¬ 
ternal veins; PC, precostal ner- 
vule; UDC , MDC, LDC, upper, 
middle, and lower discocellulars. 
