Without a doubt, it was Fred Urquhart's undaunted perseverance that ultimately led him to the renowned wintering grounds of the magnificent monarch butterflies in 1975. Research about this amazing discovery shows that Urquhart was overwhelmed on seeing literally millions of monarchs clinging in huge masses to tall Oyamel trees in northern Mexico.
North American monarchs are already migrating en masse to their various favorite "Southern Vacation Spas" as this article is being written. However, before we join these migrating monarchs on a virtual tour to their famous southern spas, please take a slight detour with me on a short entomology tour.
To better understand the awesome migratory behavior of monarch butterflies, a review of their equally mysterious life cycle seems apropos first. Their magical metamorphosis process involves four distinct stages in their short life cycle: the egg, the larva (caterpillar), the pupa (chrysalis), and the adult.
Stage 1 -- Monarch eggs
The female monarch lays her fertilized eggs on the undersides of milkweed (asclepias) leaves. Her eggs are ivory-white in color and are no larger than the size of a pin head. It is quite common knowledge that she lays her eggs only on milkweed leaves because this is the ONLY food source her picky caterpillars will eat.
Stage 2 -- Monarch caterpillars
During warm weather, the monarch butterfly's eggs will usually hatch within three to five days. The caterpillars (larva) that emerge from her eggs measure less than two millimeters, but have a gargantuan appetite. Monarch caterpillars are yellow, black, and white striped, making them quite easy to identify as they almost frantically munch away on their daily diet of milkweed leaves. During this time they grow very rapidly, and as they grow they shed their skins (or molt) several times.
Stage 3 -- Monarch pupa
Following another two weeks or so, the full-grown monarch caterpillar slowly becomes inactive as it prepares to enter its third life stage--the pupa (chrysalis) stage. The next critical task the caterpillar faces is to find the best location for pupation, which for monarch caterpillars is on the milkweed plant. When satisfied with the location, the caterpillar then cleverly weaves a thick silk web to attach itself to, then grasps this web with its rear prolegs. After a day or so, what is known as "pupal skin" begins to form under the last layer of the caterpillar's old skin. Ultimately this last layer of old skin splits, the pupa emerges, and is then able to attach itself to the silk web. By this time the pupa is usually disengaged from the old skin.
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