The spring Monarch Butterfly migration passed without a
single Monarch sighting at Blue Jay Barrens.
My earlier disappointment has been abated with a summer season Monarch
count surpassing any in recent years.
The Milkweed stands are receiving frequent visitations from this
colorful butterfly.
Of course, this is the real reason for maintaining patches
of Milkweed plants. Monarch larvae are
Milkweed eaters. Recent declines in the
Monarch population make it more important than ever that this plant be readily
available.
Having Milkweed plants snug up against the house makes it
easy to monitor the progress of leaf eating insect larvae. Because of a beating they took during a
spring thunderstorm, a few of the plants are unable to maintain an upright
position. Most, however, are standing
tall, even though a few needed some propping up and stem support to achieve
this condition.
Landscape designers probably wouldn’t recommend crowding the
entrance to your home with seven foot tall Milkweed plants. I would agree, especially when the flower
visiting bees during the day or moths at night get sucked into your home every
time you open the door. This Milkweed
thicket was not actually intentional. A
single plant that became established beside the water garden was allowed to
remain. Within a couple of years that
one plant became two dozen. For the
benefit of the Monarchs, I let them remain.
I must admit that I am also fascinated by the vast array of insects
attracted by these plants.
I’m currently finding larvae of all ages. The youngest are just beginning to show their
characteristic black filaments. Small
larvae are easiest to see by looking from below a sunlit leaf.
Midsized larvae show short stubs where the long black
filaments will eventually be. Larvae can
also be located by examining holes in the leaves. Feeding sites are more regular in appearance
than hail damage left by the early storm.
Leaf damage causes the Milkweed plant to ooze its thick
white sap. The sticky sap can make it
difficult for the larva to feed. The
larva overcomes this obstacle by systematically severing the veins leading to
the leaf, this stopping the flow of sap.
In small leaves, the midrib is often cut to halt sap flow to
the entire leaf. On larger leaves, a
series of lateral veins might be cut as seen here.
Once the sap stops flowing, eating commences.
The larvae seem to practice an eat-and-run technique that
minimizes time spent in any one location.
A section of leaf is consumed and then the larva moves on to another
location. Many predators are attracted to
leaf damage in search of prey. Despite
the Monarch’s unpalatability due to accumulating toxins from the Milkweed plant,
some predators have to learn the lesson first hand to the detriment of the
larva. Even though they are bad to eat,
the best survival strategy is to avoid the predators.
The excess rainfall experienced this spring has really
benefited the Milkweeds in the field.
The plants bloomed early and are continuing to produce new flower buds.
This large stand of Purple Milkweed continues to attract
Monarch Butterflies as well as other insects dependent on the Milkweed plant
for their survival.
It appears that Blue Jay Barrens will contribute a large
number of Monarchs to the masses that will make their way south later this
summer. I just hope that conditions at
their wintering grounds are favorable for the species continued survival.
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