1890 .] 
91 
[Packard. 
about the same as that of the reddish lateral line in which it is sit- 
uated.” While usually evaginated to a distance of about 75 mm., 
if it is greatly disturbed, “the organ is sometimes further evagi- 
nated, a moment only, to over a millimetre in length.” Dimmock 
thinks that the organ is probably “the opening of a gland, although 
it never appears moist.” He does not compare these glands to the 
dorsal eversible glands of Orgyia, but they are undoubtedly hom- 
ologous, though those of the present group do not present such a 
striking contrast in color with those of Orgyia. Dimmock thinks 
“their function may be to drive away some parasite, for against the 
attacks of ichneumons the sharp spines of this larva are an inade- 
quate defence (p. 353). He then adds that it must be of interest 
to note whether the larva possesses these organs in all its different 
stages.” 
Having alcoholic specimens of this caterpillar in different stages 
I have been able to detect them, and can state that they undoubt- 
edly occur in each stage of larval life. In freshly hatched io lar- 
vae (judging from my alcoholic specimens, where, however, 
they may be in different degrees of contraction) the glands seem 
larger in proportion than in the mature larva. They are in stage 
i spherical and white, and those on the first abdominal are larger 
than those on the seventh abdominal segment, being about as large 
as the swollen base of the largest spines. They were also detected 
in the third or fourth and the last stage. 
Since the above account was sent to the Society, I have observed 
these glands in stages i-iv of the living larva. They are flesh- 
colored, and when the caterpillar is touched it instantly everts a 
pale whitish flesh-colored spherical gland, and very soon, after the 
stimulus is removed, retracts it. When the gland is retracted what 
projects beyond the skin is irregularly hollowed in the middle. Ob- 
serving them in a large larva of stage iv with its broad lateral flesh- 
£5 0 0 
colored band, the glands are seen to be of the same general color 
as the reddish band, but clearer, while the eversible portion is 
whitish. 
Eversible glands of an io-Uke larva from Cordova , Mexico . — 
While at Cordova, Mexico, in March, 1885, I hastily picked this 
larva off a tree or shrub of unknown species in a coffee plantation. 
The alcoholic specimen is about two inches long ; it is blackish, with 
no lateral reddish line ; the spines are somewhat like those of H. io , 
but are longer, especially those on the thoracic and last abdominal 
segments and are pale throughout, contrasting with the dark bod} r . 
