DISPERSION" OF GIPSY-MOTH LARV^S 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. 

 (PI. I, fig. 2, b.) The term "aerophore" previously applied to the 

 swellings on the short hairs is misleading, as is also the term a toxo- 

 phore" suggested by Cholodkovsky. The term "acuminate" still 

 applies to the very long slender hairs. (PI. 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 

 swelling's which sometimes extend above and below the latter. The 

 air globules and liquid columns alternate in hairs of dead larvse, 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 larvse 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 1 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 

 type- of hairs — probably those ruptured during the dissection. 



After some experience it is easy with the aid of a high-power 

 ini-< tm-co pc to recognize the difference in refractions through the 

 walls of hairs full of colorless liquid or containing globules of. air and 

 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 iii aspect is noted in dead larvse 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 sulphuric acid. After six 

 bours man) of the larvae were <\c;n\ and upon examination a large 



