MEMOIRS OF THE iTATIOXAL ACADEMY OF SCIENCES. 
15 
Origin of the lines, — As Weismann lias shown, tlie primitive markings of caterpillars were 
lines anti loiigitmliual bands, the spots appearing from interruptions or what may be called the 
serial atrophy of the lines or bands. It is not difficult to account for the origin of the dorsal line, 
as this would naturally be due to the presence of the heart underneath. This dorsal line is, for 
example, wanting in the freshly hatched larvie of Spilosoma virginica and Hgphantria iextor^ but 
after the first molt of S, virginica there is a slight, diffuse dorsal line of no decided color, though 
after the second ecdysis it is decidedly whitish, or at least much jialer than the surrounding dorsal 
region. In pale catei'iiillars the dorsal line may be darker. In the first stages of the two moths 
in question there are no lines or bands j only the luliferous warts. Whether the subdorsal or the 
spiracular lines were the first to origiuale is uncertain, but probably, from Avhat Weismann has 
concluded from his studies of the Sphingidte, the subdorsal arose first. In the second stage of' 
Spilosoma virginica the subdorsal lines are reddish lines extending between the two subdorsal 
rows of alternating subdursal piliferous warts, the line becoming more decided, however, in the 
third stage of this species, there being as yet no signs of a spiracular or of any lateral line. In 
the freshly hatched larva of JI. textor^ however, what maybe the first beginnings of the subdorsal 
line are elongated brownish linear spots inclosing the subdorsal row of larger piliferous dots, but ■ 
not reaching the sutures between the segments. These patches, however, do not in the second 
stage unite to form continuous lines, but two rows of decided black elongated spots inclosing 
the black i>iliferous tubercles. In the freshly hatched larva of Edema alhifrons each of the two 
subdorsal lines is a row of elongated black spots connected on the three thoracic segments, but 
separated by the sutures along the abdominal segments. 
The si)iracular line is seen in the same larva of the same stage to be a yellowish baud inclosing 
the spiracles, and there seems to be a tendency in some, if not many, larvie for the spiracles to be 
inclosed and connected by a parti-colored or bright line, and for this to have a darker (as in Edema} 
or lighter edging. Why the spiracles themselves are so apt, as in Bombyces and Sphinges, to be- 
inclosed by a dark or cousi>icuous line remains to be explained. 
To return to the subdorsal lines in the pale-reddish larva of Datana, probably D, integerrima^. 
these lines before the first molt are also inclosed by the two rows of subdorsal j^iliferous si)ots, 
and in both the first and second stages there are pale spiracular lines, which appear to be contem- 
poraneous with the subdorsal line. In the third stage a new dark-red line is interpolated between 
the subdorsal and spiracular. In the fourth stage the spiracular line has disappeared, and there 
is a supra and an infra* spiracular pale line on the now brown, dark skin of the caterpillar. Seen 
fi’om above there are four pale lilac lines, but after molting two of them disappear, and in the 
last stage there are only two subdorsal lines to be seen, if iny colored drawings, very carefully 
made by Mr. Brigham, are correct. We thus see that after the subdorsal and spiracular lines are 
formed, others are rapidly introduced — and some may as rapidly vanish, as necessary features of' 
certain stages — which, when they become useless are discarded. 
The admirable and most suggestive work of Weismann has placed on a sound basis the theory 
of the origin of the lines, bands, and spots of the Sphingidie. The additional notes by Professor 
Meldola and the beautiful researches of Mr. Poultoii have abided to the strength of the arguments 
of Weismann. The lines, bars, stripes, spots, and other colorational markings of caterpillars, by 
which they mimic the colors and shadows of leaves, stems, etc., have evidently been in the first ])lace 
induced by the nature of the food (chlorophyll), by the effects produced by light and shade, by 
adaptation to the form of the edge of the leaf, as in the serrated back of certain Notodontians, by 
adaptation to the colors of different leaves and to the stems, often reddish, shades of greens, yellows, 
reds, and browns being as common in the cuticle of caterpillars as on the surface or cuticle of the 
leaves and their stems or in the bark of the twigs and bi'anches. We (and jirobably others) have 
obsei'ved that the x^eculiar brown spots and patches of certain Notodontians do not appear until, 
late in larval life, and also late in the summer or early in the autumn contemporaneous with the 
appearance of dead and sere blotches in the leaves themselves. 
Now, to say that these wonderful adaptations and marked changes in the markings of cater- 
l)illars are due to ‘‘natural selection,” and to let the matter rest there, is quite unsatisfactory. 
Natural selection may account for the elaboration of these larval forms with their markings after- 
they have once appeared, but we Avant to discover, if possible, the original causes of such orna- 
