Monarch Butterfly Development


I have seen several recent items about the Pollinator Pathway initiative and Monarch butterflies. Professor Trumbo had an informative item [Sept. 17] about the Monarch. I recently found a Monarch caterpillar that had attached to a stem of a potted Fountain Grass in my yard, and it was about to form a chrysalis. It probably grew on a nearby Swamp Milkweed. I took the photos here from Aug. 27 to Sept. 5, documenting the development cycle.

The last stage caterpillar attaches itself to a plant stem [need not be a milkweed] and curls into a J-shape. Soon, it forms an outer “shell” for the chrysalis. In early chrysalis stages the caterpillar’s stripes can be seen inside the chrysalis. Over the next few days the pattern changes. When the color goes dark, emergence is only a few hours away.

Soon visible through the “shell” is the black and orange pattern of the adult. The bottom of the clear chrysalis opens and the adult emerges with wings and body not yet in their final shapes. For our Monarch, that happened about 11:55 a.m. on Sept. 5. Hanging from the chrysalis, the adult pumped fluid into her wings, expanding them. By 2:40 p.m. the female adult was ready to fly. A few flaps and she was gone.

Professor Trumbo noted the importance of the knowledgeable backyard gardener. Recent research found that store-bought milkweed plants were contaminated with toxic chemicals [fungicides, herbicides, insecticides] that could harm the Monarchs and other pollinators. Plants grown from seed should be OK. One suggestion is to cover the nursery plants the first year. The next year the pesticide residues should be reduced. Wind-borne spray may also cause problems. I am interested in all our insects and preservation of biodiversity. Here on Yoda Brook, the only spray we use is a mix of vinegar, salt, and detergent. Some references are [a summary on] and various materials on [].

— Photos and notes by Karl Eric Tolonen


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