122 NATURE SKETCHES IN TEMPERATE AMERICA 



Monarch Viceroy 



Egg unlike Viceroy, often parasitized Egg unlike Monarch in shape and 

 by small hymenopterous insects, reticulations; often parasitized by 



Triehogramma intermedia. Triehogramma minuta and T. minu- 



tisaima, the two being hymenop- 



terouS| insects. 



Caterpillar when full grown presenting Caterpillar when full grown often 



lemon-yellow bands with shining mottled grayish and white (see 



black, and provided with a pair of plate illustration), supplied with 



fleshy filaments on second thoracic prothoracic and other spinous 



and seventh abdominal segments; tubercles; parasitized by ichneumon 



often parasitized by ichneumon flies. flies. 



Generally unlike Viceroy in form and Generally unlike Monarch in form 



coloration. and coloration. 



Feeds on species of milkweed exclu- Feeds on willow, poplar, etc., but 



sively. never on milkweed. 



Pupa stout, cylindrical, pale green. Pupa slender, obscure gray, the 

 ornamented with golden spots. middle of dorsum with a projecting 



boss. (See plate illustration.) 



The first thing to note in the above brief comparisons is 

 that only during the adult butterfly stage is there any resem- 

 blance between the two species, there being no trace of mimicry 

 in either the egg, caterpillar, or pupa stages. Why is this 

 mimicry confined to the adult stage ? I have already shown 

 that the two species are associated only during the adult life 

 when feeding on flowers, and at no other time. Here is a sig- 

 nificant suggestion in the answer to our inquiry. Are the adults 

 especially exposed to the attacks of birds and lizards? The 

 Monarch is said to be protected from these attacks by the 

 presence of distasteful scent scales on the hind wings of 

 the male, and the Viceroy is supposed, by virtue of its close 

 resemblance, to share the same immunity. 



Though theoretically thus protected, there are very few in- 

 stances recorded where the Monarch and its mimic are attacked 

 by birds, and for this reason some observers have thought the 

 mimicry here is a coincidence. In August, during four seasons, 

 I have seen the Monarch gather in swarms on the branches 

 of cedar and. on the leaves of the beech trees. While these 

 congregations took place, lasting perhaps for a week or more, 

 I could not discover that one of them was destroyed by 

 migratory or resident birds. All the individuals constituting 



