FALSE PARASITES. 107 



leader returning to its nest. The larger caterpillars' deposit 

 fseces in the nest, which, falling among the threads of the cocoon, 

 render the latter more opaque, and more capable of resisting 

 external influences. This closing up happens usually at the end 

 of July or beginning of August. Each caterpillar prepares for 

 itself a separate case or cocoon inside the large cocoon, which is 

 of a grey-yellow colour and silk-like appearance. The single 

 cocoons of the caterpillars resemble, in the method of their spin- 

 ning, that of Bombyx mori : they are, however, more oval, 

 smaller, and very rich in the yellow powdery substance, of which 

 we shall have to speak. The cocoons are formed in one night. 

 The butterfly escapes towards the end of August, by softening 

 the threads of its cocoon with its saliva, (?) and thus dissolves 

 them. It copulates, lays eggs, and dies. Many of the chrysa- 

 lides in the cocoons were destroyed by white, worm-like, hairless 

 parasites. 



The inhabitants of Westphalia are well acquainted with the 

 important and dangerous diseases and sufferings which are caused 

 by these caterpillars both in men and animals. It is very 

 doubtful whether the noxious substance which acts like a poison, 

 creating redness, itching, and burning of the external and in- 

 flammation of the internal parts, and causing even death, con- 

 sists of the long hairs of the caterpillar. According to some 

 writers, the nest or cocoon is to be looked upon as the cause of 

 these disorders ; whilst others say that they are caused by an 

 acrid noxious juice which the caterpillar is thought to secrete 

 when it creeps over the surface of the skin. Nicolai convinced 

 himself of the impossibility of the latter cause, for he observed 

 itching pustules on his forearms which were covered with clothing, 

 though the caterpillar had never come near them. On one 

 occasion, when attempting to attach to a board a large caterpillar 

 by means of pins, and for this purpose piercing its black back 

 shield, he saw on the edge of the shield a reddish-yellow, fine, 

 dust-like, saffron-coloured powder proceed from the shield, without 

 the latter being altered in the least. The interior of this spot 

 showed no especial organ nor opening. Later observations, 

 however, are said to have discovered underneath these reddish 

 spots two large warts which almost touch one another, and 

 which are especially noticed when the caterpillar casts its skin 

 and has become deprived of its hair. The same dust was found 

 by Nicolai in the nests and cocoons in the parts which surround 



