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, 

 with their two upper surfaces in 

 proximity, the under surfaces alone 

 displaying their colors to the eye. 

 Only in a few genera of the larger 



Fig. 40.— Wing of Anosia plex- 

 ippus, showing the names of the 

 Veins and nervules: C, C, costal 

 veins; SC, subcostal vein; SG.etc, 

 subcostal nervules; UR, upper ra- 

 dial ; LR, lower radial ; M, median 

 veins; Mi, M%, A/3, median ner- 



. . vules ; SM, submedian veins ; /, in- 



butterflies, and these tropical species, temal veins; PC, precostai ner- 



with which this book does not deal, vule; UDC, MDC, LDC, upper, 



. , ., • , middle, and lower discocellulars. 



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 



