\(\-2 GYPSY AND BROWN-TAIL MOTHS. [Jan. 



in water there is no slowing of their reaction with the red blood cor- 

 puscles. 



In distilled water the nettling hairs remained active after a period 

 of eighteen days, even though during this time they were eentrifugal- 

 i/.fil and washed several times, in addition to being placed in the incu- 

 bator at 38 C. for sixteen hours. When wanned in distilled water to 

 50 C. they were still active, but when warmed to 60 C. they im- 

 mediately failed to react. Since the substance which gives the reaction 

 withstands much higher temperatures, it seems reasonably certain that 

 it is dissolved out in water raised to this temperature. 



Inasmuch as the poisonous substance was evidently soluble in fluid 

 blood at room temperature, it seemed plausible that it might be soluble 

 in dilute alkaline solutions. This was found to be the case. Both 1 

 per cent, and _L per cent, solutions of potassium hydrate and sodium 

 hydrate in distilled water were used. The nettling hairs, after remain- 

 ing over night in these solutions at room temperature, failed to act 

 cither on the skin or on the red blood corpuscles. 



From these data it seems necessary to conclude that the nettling 

 hairs possess a substance which acts as an irritant to tissues (epidermis) 

 which is relatively stable, being destroyed by heating at the temperature 

 of 115 C. or over, and which is quite soluble in dilute alkalies at room 

 temperature or in water wanned to 00 C. I have been unable to dem- 

 onstrate whether this substance is located within the nettling hair, or 

 carried upon the surface at its point. If it is true that the wall of the 

 nettling hair is perforated at this point, as indicated by the penetra- 

 tion of staining fluids, it seems not unlikely that the poisonous sub- 

 stance is contained within the chitinous walls. This is borne out by 

 the activity of these hairs after soaking two and a half weeks at room 

 temperature in water, a reagent which is known to be a solvent when 

 raised to 60 C., for it seems improbable that so small an amount of 

 the irritating substance, as there must necessarily be, could remain un- 

 dissolved for this length of time if smeared on the surface of the hair. 

 Furthermore, the specific reaction with the red blood corpuscles always 

 begins at the point of the hairs, except in instances in which they are 

 broken, when the reaction takes place rapidly about the point of frac- 

 ture. If the irritating substance was secreted, as certain observers have 

 believed, by the two retractile tubercles on the hinder segments, and 

 smeared by the movements of the caterpillar over ils haii-s. the coarse 

 hairs also would have nelt lini;- properties, and react with the red blood 

 corpuscles; but such is not the case. It is probable that the protection 

 afforded the irritating substance by its inclusion within cliilinons walled 

 tubes and also its chemical stability account for the fact that the net- 

 tling hairs remain active for long periods of time, unaffected by natural 

 influences, such as fluctuations of temperature or repeated wetting and 

 drying. 



Since it was impossible to obtain caterpillars in sufficiently large num- 



