with its tentacles retracted, and this resem- 
blance is enhanced by the flesh-like aspect 
of the whole extended portion of the organ, 
its color being about the same as that of 
the reddish lateral line in which it is situ- 
ated. The organ is usually evaginated, 
as above described, upon any slight distur- 
bance of the larva, toa distance of about 
7) mm. 4 
If the larva is greatly disturbed, espec- 
jally suddenly, as by a sharp, quick stroke 
on the spines.or by a pinching of the skin, 
the organ is sometimes further evaginated, 
a moment only, to over a millimetre in 
length. The distal extremity, when fully 
eyaginated, is rounded, being terminated 
by a hemispheroidal portion of more deli- 
cate texture and of slightly lighter color 
than the proximal portion. 
This organ is probably the opening of a 
gland, altho it never appears moist. The 
abundant moisture, however, which usually 
indicates glandular secretion in insects is 
not a necessary character of such secretion, 
any more in insects than in vertebrates. 
Silk and the woolly masses on aphides are 
examples of nearly dry solid secretions in 
insects, while the gas, permanent under 
ordinary conditions, which is emitted from 
the anal glands of Brachinus shows that 
an insect secretion may either be gaseous 
or become gas directly upon its emission. 
So the absence of appreciable moisture is 
‘no sure proof that the organs under consid- 
eration are not glandular. There is no 
odor about these organs, as far as I could 
determine, nor did their surface show either 
acid or alkaline reaction upon being touched 
with moistened litmus paper. — 
The function of these organs seems to 
be to defend the larva, already s6 thoroughly 
PSYCHE. 
309 
protected from many dangers by its urtica- 
ting spines, from some kind of attack, for 
the organs are not in use when the larva 
is undisturbed and are more active in their 
protrusion and retraction the more the 
larva is disturbed. Their function may 
be to drive away some parasite, for against 
the attacks of ichneumons the sharp spines 
of this larva are an inadequate defense. 
The improbability of four such organs 
as those described above escaping the notice 
of all the entomologists who had carefully 
examined the larva of Hyperchiria varia 
led me to look up all the accessible descrip- 
tions of that larva, but I found no mention 
of these organs in any of them. Harris, 
in his Entomological Correspondence,’ and 
Riley, in his Fifth Report,’ give quite 
extended descriptions of the larva and locate 
the different series of spiculiferous tuber- 
cles, but entirely overldok the organs which 
are the subject of this note. 
As I have neither time nor material for 
the extended study of these organs I pub- 
lish this brief note on their external appear- 
auce in the hope that some one will study 
them further, especially in regard to their 
internal structure and to determine their 
functions with certainty. It would be of 
interest to note whether the larva possesses 
these organs in all its different stages, a 
point which I was unable to settle because 
of having no very young larvae. 
Cambridge, 7 Sept. 1882. 
1 Occasional papers of the Boston society of 
natural history. 1. Entomological correspon- 
dence of Thaddeus William Harris, M.D. Edi- 
ted by Samuel H. Scudder. Boston, 1869. p. 
295-297. ; 
2 Fifth annual Report on the noxious, benefi- 
cial and other insects of the state of Missouri, 
...by C. V. Riley, state entomologist. Jeffer- 
son City, 1873. p. 135. 
‘ 
