by Linda S. Ellis
|Baltimore checkerspot web|
The hatchling larvae climb to the top of the plant, in this case the false yellow foxglove, and begin to spin an increasingly dense web nest as they feed on the foliage. The problem with having such a conspicuous abode is the nest is liable to be torn or destroyed by a passing deer or hail storm and it isn’t hard for predators to spot such a collection of goodies, either. Parasitoides can and do lay eggs into the resting larvae right through the webbing. Larger predators, such as blue jays, avoid these caterpillars since feeding on plants in the snapdragon family give them a toxicity similar to the monarch/milkweed association.
The young larvae live gregariously, moving around the host plant by day but returning to the web for rest or diapause. As the individuals develop, they molt right inside the webs and go through 4 stages of growth or instars. When they reach the 4th stage, some time in the fall, they travel down the plant and build a different kind of silk shelter in the leaf litter to over-winter.
In spring, the 4th stage larva supposedly seeks out the same plant types it fed on as a younger caterpillar but, in my experience, the larvae never showed up again on the false yellow foxglove but sought out the wood betony (Pedicularis canadensis) plants in the area. I suspect this is because wood betony or louse wort (who names these things?) is available early on which to feed while the other Scrophulariaceae emerge later in spring.
Since that first encounter in 1999, I have followed the seasons of the Baltimore checkerspot where I first discovered them. Some years they were abundant and predictable in their appearance and some years sparse or found on alternate plants. During the flooding of 2008, the nearly constant rain destroyed the web nests and I wondered if they would disappear from the area. I found the checkerspots again in 2009 on mullein foxglove (Dasistoma) this time. This plant tends to grow in more sheltered areas beneath trees along creeks and waterways and one can conjecture it would be a less hazardous place to exist than the habitat of false yellow foxglove which prefers dry forest openings.
|Adult taking nectar from purple
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