62 GROTE—THE DESCENT OF THE PIERIDS. [Jan. 5, 
second ; the first is also the first to disappear, followed by the fourth 
and third. 
The humeral spurs of the Lachneidz have been cited as examples 
of specialization by addition in the wings of the Lepidoptera. This 
may have been their origin. ‘They appear to attain their maximal 
development on the secondaries of utricha quercifolia (consult 
Grote, ///. Zeits. f. Entom., Band 4, Heft 4, Fig. 1). In the diur- 
nals the spurs would be already reduced to a single one. But even 
in the Lachneids the generic types I have examined have them very 
unequally developed. And they may have appeared independently 
in different groups. The repetition of the neuration, as might be 
expected in homodynamic organs like the wings, is, so far as I 
know, always exact. Slight variational changes in the position of 
the veins, following the general directions of specialization, are re- 
peated on both sides of the insect. Accidental aberrations, fail- 
ures in development, are of unequal, local origin and have a special 
cause. The two classes of individual deviation from a given type 
should be discriminated. 
The bending inwardly of 4 3 on the secondaries of E/odina 
exnatia (Fig. 10) leaves a wide, unsupported lobe at the base of the 
wing, which seems to be traversed by an irregular, linear thickening 
of the membrane, having the false appearance of avein. ‘This 
would be secondary and its origin analogous with that of the hume- 
ralspurs. But the feature must be studied from more material than 
at the moment is at my disposal. It is possible that the last anal 
vein (4 4) in Pseudopontia, marked in my figure ‘‘ix,’’ is homolo- 
gous with this thickening in A/odina ; in both 4 3 is bent inwardly. 
Compare these PROCEEDINGS, xxxvii, No. 157, Pl. i, Fig. 7. 
ACKNOWLEDGMENTS. 
After wandering for nearly forty years in the wilderness of but- 
terflies, it may be the last time I have the opportunity of expressing 
my indebtedness to other students and their works. And first I 
return thanks to Prof. Comstock for the assistance which his publi- 
cations on the wings of the Lepidoptera have been to me, no less 
than for his kind communications upon debatable points. Prof. 
Comstock has worked out, with immense patience and labor, a sys- 
tem of notation applicable to the veins of all insect wings, and 
which is here adopted for the butterflies. Thus the original idea of 
Redtenbacher, who must not be forgotten, has, I hope, received its 
