Phylogeny of the Pierine. 275 
nervules, S 18 appears as a submarginal spot of the usual 
kind. Now, inasmuch as no member of series D ever 
occupies this interspace, there is no material at hand for 
continuing the streak ; and, carrying the eye up to the 
apex of the interspace, where the streak should cross, 
we find it, in fact, deficient at that place.* This may 
seem a small point, but it is of interest as illustrating 
the absence of anything that might be called violent or 
arbitrary in the evolution of these various patterns, in 
which, indeed, the closer the examination the more 
difficult it is to find anything effected per saltwm. 
In Jzias the condition is again much the same as in 
Colias ; the discoidal spot of the forewing, however, is 
often united on the upper surface with a dark band 
running across the wing from the costa to the anal 
angle. A similar feature occurs in Hebomoia glaucippe 
(Fig. 19) and other species of the same genus. On the lower 
surface the discoidal spot varies considerably in size, and 
in a few cases (as sometimes in I. marianne) may be 
absent altogether. When it is large, as in other 
specimens of I. marianne, it is frequently centred with 
white. In the hindwing the series is absent from the 
upper surface, and represented below only by D 4, which 
may also be white-centred, or may exist as a simple 
black dot of varying size. 
In Teracolus, D is usually well marked. In some 
species, such as 7’. vesta, T’. hewitsonii, and T’. puellaris, 
it occurs on the forewing as a conspicuous black patch 
covering both disco-cellular nervules, and usually merged 
anteriorly in a dark or dusky band which extends along 
the costal border. In other species, as 7’. evanthe, T’. ione, 
T. regina, etc., it takes the form of a circumscribed black 
spot, sometimes minute or absent. On the lower surface, 
the scales on and surrounding the disco-cellular nervules 
are often whitish, thus giving Da pale centre. D in the 
hindwing, when present, is usually small; on the under- 
side of some species, as 7. danae, T. evippe, and 1". 
omphale, it is centred or shaded with orange ;—this 
tint belonging primarily to the disco-cellular nervules, 
and spreading more or less widely from them. 
* As above noted (p. 260), the corresponding streak in the fore- 
wing of P. trite, and the somewhat similar feature on both wings 
of Dercas lycorias, are entirely formed out of series 8. 
