PSICHE. 398 
salicylic acid is an oxidation-product. 
Claus says that the larva of Lina populi 
has been used as a source of salicylic 
acid in small quantities. The odorous 
secretion of the glands of the larva of 
_ Lina protect not only the larva, but, as 
Lyonet noticed, also the pupa, from the 
attacks of birds. Claus shows how this 
protection of the pupa is accomplished : 
the glands, with their contents, are shed 
with the last larval skin, which remains 
around the point of attachment of the 
abdomen of the pupa, and, when the 
latter wriggles about on account of any 
disturbance, the odorous fluid is squeezed 
from the molted glands. De Geer* de- 
scribes and figures the spines of the 
larva of Lina populi in 1775. Lyonet,* 
probably somewhat earlier, describes and 
figures the larvae of Lina populi and L. 
dorsalis, and mentions the protrusion 
and retraction of the milky drops. 
Ratzeburg*® mentions briefly the glan- 
dular secretion of ZL. populi, and West- 
wood* collects together notes on the 
larvae of different species of Lina. 
Chapuis and Candéze* write that the 
larva of Lina (Plagiodera) scripta from 
the United States is similar to that of 
L. populi. 
Claus* was the first to study the in- 
ternal anatomy of the glands and spines 
of -Lina populi, and he shows that the 
liquid is pushed out of the spines by 
a contraction, which I may be allowed to 
term an incipient evagination, of the 
walls of the gland. This leads one to 
search further in order to find if this 
principle of evagination of glandular 
walls is not carried to a greater extent 
® 
in other insects. Little search reveals 
numerous forms of glands in which a 
part or the whole of the duct, or the 
glandular surface itself is evaginable. 
This form of gland is not confined to 
any one order of insects; altho first 
found in lepidopterous larvae, glands of 
this form have since been found in ima- 
gos of lepidoptera, coleoptera and ortho- 
ptera. The latest writer who has dealt 
especially with this kind of glands is 
Klemensiewicz,* in 1883. 
In this group of glands or gland-like 
organs may be classed the evaginable 
osmateria of the larvae of Papilio, the 
protrusile tails or modified anal legs of 
the larva of Harpyia (Cerura), the 
lateral appendages of Mulachins, cer- 
tain evaginable appendages upon the 
eleventh and twelfth segments of the 
larvae of some species of Jycaena, 
lateral evaginable appendages in a 
species of Corydia, the red protrusile 
warts upon the dorsum of the larva of 
Orgyia, the evaginable warts of some of 
the stinging larvae of bombycidae, the 
evaginable appendages of various forms 
near the anus of certain imagos of lepi- 
doptera and coleoptera, the organs on 
the ventral side of the first thoracic 
segment of many lepidopterous and of 
a few phryganeid larvae, and the pro- 
trusile organs near the anus of larvae of 
Myrmeleon. 
Organs of the sort now under consid- 
eration were first mentioned in 1602 by 
Aldrovandus,” who observed and roughly 
figured osmateria on the larva of 
Papilio. Frisch™* (Theil 2, p. 41-42), 
in 1721, describes the osmateria of the 
