6 BULLETIN 273, U. S. DEPABTMENT OF AGBICTTLTTJEE. 



portion of the vesicles of the hairs had buckled or partly collapsed. 

 Larvae still living at this time presented the same appearance to a 

 slight extent. As a check on this experiment, larvae were killed with 

 chloroform and after 24 hours showed a smaller proportion of buckled 

 or collapsed vesicles, indicating that sulphuric acid took up moisture 

 from the porous hairs. 



Sections were made of the larvae and cells at the base of the 

 hairs studied, but there could be found no indication of the presence 

 of glandular cells. A large trichogen, however, is present at the base 

 of each hair. This would signify that the liquid inclosed in the 

 hairs is not a toxin, as Cholodkovsky suggests, but a mere colorless 

 mobile liquid secreted during the formation of the hairs. The 

 phenolphthalein and litmus-solution tests were also tried, with nega- 

 tive results, further indicating a neutral liquid. The peculiar shape 

 of the vesicular hairs, however, suggests that they may at one time 

 have had a poisonous function but that it has been lost in the present 

 generations. 



The results of the experiments and observations indicate that both 

 the normal vesicular and acuminate hairs are filled with a colorless 

 liquid; that the hairs are hollow throughout, and that the vesicles 

 contain the same media as the remaining portion of that type. A 

 few globules of air were seen in hairs of living larvae which were no ted 

 as exceptions. Air partially replaces the liquid after death, following 

 which period the vesicles collapse. It is therefore probable, as Ige- 

 nitzky and Shcherbakov have indicated, that the acuminate hairs 

 play the greater r61e in making the larvae more buoyant, as these 

 are from four to six times as long as the vesicular hairs. 



SCOPE OF INVESTIGATIONS ON WIND DISPERSION. 



In that the main purpose of the following investigations was to 

 secure data on the maximum distance and the extent to which small 

 larvae are borne by the wind, it was necessary to find conditions 

 where an abundance of larvae were present in close proximity to 

 treeless areas. These conditions were best afforded along the beaches 

 in Massachusetts and New Hampshire, where there are stretches of 

 marshland from 1 to 2 \ miles wide and many miles long. These 

 marshlands are occasionally flooded with salt water and do not con- 

 tain vegetation favorable to the development of gipsy-moth larvae. 

 The areas selected for the experiments were to the east of the heavy 

 infestations, thereby getting all the advantages previously known to 

 accrue from the northwest, west, and southwest winds. The Isles 

 of Shoals, off the coast of New Hampshire, afforded ideal conditions 

 in so far as their remoteness from the mainland was concerned and 

 the fact that the country opposite has been infested since 1905. 

 Locations were also selected in the hills of New Hampshire near the 



