340 FS TCE: 
ASYMMETRY OF THE NERVOUS SYSTEM IN THE LARVA OF 
HARP YIA, 
BY ANNA KATHERINA DIMMOCK, CAMBRIDGE, MASS. 
NoruineG has been published in regard 
to asymmetry of the nervous system of 
arthropoda, as far as I have been able 
to ascertain. 
In dissecting a number of the larvae 
of Harpyia (Bombyx) vinula, I found 
that the nervous system, instead of ex- 
tending in a direct line in the ventral 
region of the larva, as is common in in- 
sect larvae, curved outward laterally 
between the first and second thoracic 
ganglia, as seen between c and d in figure 
6. This curving, which was toward 
the left in six larvae examined, is to 
avoid interference with the duct from a 
sac, or gland, which opens out between 
the first and second thoracic ganglia. 
This gland, represented in the figure by 
a dotted line, secretes a liquid, said to 
contain salicylic acid, which the larva 
ejects, as a means of defense, when dis- 
turbed. The duct of this gland opens 
by a transverse cleft, figured by Miiller,’ 
on the ventral side of the first segment 
posterior to the head. Further details 
in regard to this gland are unnecessary 
as a good description of it has been 
given already by Rengger.? 
In. the earlier stages of the larvae of 
Harpyia, the nervous system turns con- 
siderably out of the direct line, in order 
to allow the duct of the gland to pass, 
1 O. F. Miiller. _ Pile-Larven med dobbelt Hale, og 
dens Phalaene .. . Kjobenhavn, 1772, pl. 2, fig. 3, d. 
2 J. R. Rengger. Physiologische Untersuchungen 
iiber die thierische Haushaltung der Insecten. Tiibing- 
en, 1817, Pp. 35-36- 
as can be seen in figure 6, which repre- 
sents the condition in a_half-grown 
larva; but, in the full-grown or nearly 
full-grown larvae, the nervous systein is 
nearly straight, altho it is still distinctly 
unsymmetrical. This lessening of 
asymmetry, as the larva grows, is due 
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Fig. 6.—View of anterior portion of central nervous 
system of larva of Harpyta vinula as seen from above: 
a, supraoesophageal ganglion; 6, infraoesophageal 
ganglion; c,d, and e, thoracic ganglia; f, first abdominal 
ganglion. Dotted line represents gland mentioned in 
text. Enlarged 6 times. 
to the duct being somewhat smaller in 
larger larvae, in proportion to the size 
of the larva, thus allowing the nervous 
system to settle back, more or less, into 
its normal position. 
The commissures connecting the first 
and second thoracie ganglia (¢ and d) 
are united three-fourths of their entire 
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