158 (iVPSY AND BROAVX-TAIL MOTHS. [Jan. 



all segments I'nun the fifth t<> tin- twelfth inclusive. Patches of nettling 

 hairs are at this time also found just below the tufts of white branching 

 liaii-s on the lateral tubercles of the same segments. The increase in the 

 production of nettling hairs at this stage makes the caterpillar " poison- 

 ous" to a degree much greater than in any of its preceding molts. 



The nettling hairs developing upon the- caterpillar may eventually 

 be widely disseminated from their original source. In the process of 

 manufacturing the cocoon the hairs are all nibbed off the caterpillar 

 and enter into the structure of the cocoon. It is unquestionably by 

 reason of the nettling hairs enmeshed in and adherent to cocoons that 

 a dermatitis so often follows contact with them. Since severe dermatitis 

 has frequently followed the handling of cocoons over a year old, it is 

 evident that the irritating substance connected with the hairs is. under 

 ordinary conditions, extremely slow to disintegrate. 



Nettling hairs are found mingled with the long hairs of the brown 

 tuft on the tail of the moth where they are most numerous near the 

 distal ends, and are not found near the roots of the long, coarse hairs. 

 Although the nettling hairs are present in large numbers, especially on 

 female moths, which possess a larger and thicker tuft on the tail, I have 

 been unable to demonstrate that they have any constant anatomical rela- 

 tion to the body of the moth. Fernald and Kirkland, since they found 

 these elements in variable numbers and irregularly distributed over the 

 moths, concluded that they probably become entangled among the scales 

 of the moth as it works its way out through the cocoon, and that thus 

 all the nettling hairs are primarily derived from the caterpillar. The 

 tuft of thick brown hair on the tail of the female is deposited in the 

 form of a felt-work around the eggs as they are laid on the under sur- 

 face of leaves. As this material contains many nettling hairs, it also 

 is capable of producing the typical dermatitis. 



Since the nettling hairs, once they are dislodged from the caterpillar, 

 are blown about by any slight current of air, it seems beyond question 

 that a characteristic eruption may occur without actual contact with 

 caterpillar, moth or nests. If a susceptible individual stand during a 

 slight breeze beneath a tree well infested with these caterpillars, this 

 fact will be satisfactorily demonstrated. A rash will appear on the 

 exposed parts very soon afterward, and one may experience intense 

 itching almost immediately. The lodgment of the nettling hairs upon 

 underclothes as they are linnv to dry is probably also one of the common 

 sources of the rash. To remedy this, underclothing may be hung right- 

 side out instead of being turned, as is ciislomary, or it may be sent to a 

 non-infested district to be laundered. 



In order to determine the anatomical relation of the nettling hairs, 

 serial sections were made of several of those segments of the caterpil- 

 lar which bear the velvety brown patches corresponding to the suit- 

 dorsal and lateral tubercles. These hairs are found with the points in- 

 serted in protuberant rounded sockets, with which this portion of the 



