DISPERSION OF GIPSY-MOTH LAKViE BY THE WIND. 5 
previous investigators in that the swellings on the short hairs were 
found to contain a liquid not yet proven to have toxic properties, it 
seems advisable that they should hereafter be called vesicular hairs. 
(PL I, fig. 2, b.) The term "aerophore" previously applied to the 
| swellings on the short hairs is misleading, as is also the term "toxo- 
phore" suggested by Cholodkovsky. The term "acuminate" still 
applies to the very long slender hairs. (PL I, fig. 2. c.) 
After first-stage larvae die the swellings on the hairs usually col- 
lapse and both air and liquid are present in each type of hair and can 
be seen under a high-power microscope. A living caterpillar exam- 
ined in glycerin shows air bubbles occasionally in the hairs and 
swellings which sometimes extend above and below the latter. The 
air globules and liquid columns alternate in hairs of dead larvae, and 
the difference between the air or colorless liquid present is evident from 
the typical air refractions in the globular form that air always takes 
in a liquid; also from the capillary attraction of the liquid contained. 
Living caterpillars mounted in balsam and examined under a micro- 
scope show air bubbles in some of the hairs, but such hairs are excep- 
tions rather than the rule. Caterpillars that have been dead several 
days show the opposite phenomenon — both air and liquid are seen in 
them, but air predominates. Some larvae that had been dead for 
two years were examined and these contained small short columns of 
liquid, but air filled the greater portion of the hollow spaces of the 
hairs. Practically the same was noted in the hairs of an exuvium 
from a first-stage larva which had also been kept about two years. 
The vesicles on the hairs had buckled or collapsed and contained air, 
which was later practically all driven out by heating. 
Embryos were dissected from the chorion under balsam and 
glycerin and then examined in these media. No air globules or 
what could be termed air refractions were noted in either acuminate 
or vesicular hairs. Many of the vesicles are only partially distended 
in this stage. Embryos dissected from the chorion in air contained 
air globules and columns of liquid alternating in a portion of both 
types of hairs — probably those ruptured during the dissection. 
After some experience it is easy with the aid of a high-power 
miscroscope to recognize the difference in refractions through the 
walls of hairs full of colorless liquid or containing globules of air and 
i columns of liquid alternating. The typical liquid refractions are 
always seen in uninjured vesicular and acuminate hairs. Only 
rarely are there air refractions noted in either type on living larvae. 
A decided change in aspect is noted in dead larvae after the vesicle 
begins to collapse, at which time air finds its way into the hairs. 
A number of living larvae were placed under a bell jar which con- 
tained a small amount of concentrated sulpjiuric acid. After six 
hours many of the larvae were dead and upon examination a large 
