100 Species to Know by Sight - #6 Monarch Butterfly and #7 Viceroy Butterfly

There are some species of plants and animals that every student (and adult) should be able to identify by sight.  Some species are specific to a certain region, other species are found over a very broad territory.  The sixth species on my list of 100 Species to Know by Sight is the Monarch Butterfly (Danaus plexippus).  The Monarch can be found across most of the United States and Southern Canada and is one of the most recognized (and loved species) found across its range.

The Monarch is a very distinctive, large (3.5 to 4 inch wingspan), orange-and-black butterfly. 

Monarch Butterfly on New England Aster

Monarch Butterfly - this butterfly was probing the surface of a county road with its proboscis to obtain salts and other minerals

Monarch Butterfly on a Common Milkweed flower.  This species is its larval host plant.

 
Male and female butterflies are easy easy to distinguish.  Males can be identified by the presence of a scent gland on each of their hind wings.

Monarch Butterfly - the arrows point to the pair of scent glands on its hindwings

Monarch Butterfly - the scent glands are also visible from the underside of the wing

In Mid-Michigan (really across most of its range) there is only one butterfly species you could possibly confuse with the Monarch - the Viceroy (Limenitis archippus).  The color pattern of the Viceroy is almost exactly the same as that of the Monarch.  The two species share a type of mimicry known as Mullerian mimicry in which two (or more) distasteful, poisonous, or otherwise harmful species have evolved to look like each other.  Because the Viceroy and Monarch share this relationship, the Viceroy is my seventh species on my 100 Species to Know by Sight. 

The Viceroy is typically smaller than the Monarch with a 3 to 3 inch wingspan, but there can be a size overlap in the two species.  To identify a Viceroy look for a semi-circular line that extends across its back pair of wings.  To me, this line looks like a smile.  The Monarch lacks this line.

Viceroy Butterfly- the arrow points to the line that distinguishes this species from the Monarch

Viceroy - this identifying mark is visible on both the upper and lower surfaces of the wing