501 
[Packard. 
Noctuidse, and sometimes in the Bombycidse, and always present 
in the boring larvae of the Hepialidae and the Cossidae. 
As tactile hairs, defensive or locomotive setae, and spines of man- 
ifold shapes occur in worms, often arising from fleshy warts or tu- 
bercles, it is reasonable to assume that the piliferous warts of 
lepidopterous larvae are a direct heirloom of the vermian ancestor 
of the insects. In our primitive caterpillar, then, the piliferous 
warts were present, eventually becoming arranged as they now are 
in ordinary Tineid, Tortricid, Pyralid, Geometrid and Noctuid 
larvae. 
Origin of the green color of caterpillars.— -The cuticle may at first, 
as in that of case-worms and Panorpid larvae, have been colorless 
or horn-colored. But soon after habitually feeding in the direct 
sunlight on green leaves, the chlorophyll 1 thus introduced into the 
digestive system and into the blood and the hypodermal tissues, 
would cause the cuticle to become green. Afterwards by farther 
adaptation and by heredity this color would become the hue in gen- 
eral common to caterpillars. Moreover some of the immediate de- 
scendants of our primitive caterpillars were probably lighter in hue 
than others ; this was probably due to the fact that the lighter col- 
ored ones fed on the pale-green underside of the leaves ; this dif- 
ference becoming transmitted by heredity. 
Origin of the lines . — As Weismann has shown, the primitive 
markings of caterpillars were lines and longitudinal bands, the spots 
appearing from interruptions or what may be called the serial atro- 
phy of the lines or bands. It is not difficult to account for the ori- 
gin of the dorsal line as this would naturally be due to the presence 
of the heart underneath. This dorsal line is, for example, want- 
ing in the freshly hatched larvae of Spilosoma virginica and Ily- 
phantria textor ; but after the first moult 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 paler than the sur- 
rounding dorsal region. In pale caterpillars the dorsal line may 
be darker. In the first stages of the two moths in question there 
are no lines or bands ; onty the piliferous warts. Whether the sub- 
dorsal or the spiracular lines were the first to originate is uncer- 
1 See the important and quite conclusive footnote by Professor Meldola on p. 310 
of Weismann’s Studies in the Theory of Descent, vol. I ( “ I have already given rea- 
sons for suspecting that the color of green caterpillars may be due to the presence of 
chlorophyll in their tissues, Proc. Zool. Soc., 1873, 159.— it. M.”) 
