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Macrophyte Herbivory

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In CSW, there is an abundant emergent macrophyte that I am unable to identify. It hasn’t flowered yet and the key in Crow’s Aquatic Plants of Palo Verde National Park and the Tempisque River Valley hasn’t been much help. If someone knows right away what this plant is, please let me know.

I’ve identified it to Thalia geniculata. Only the leaves are present currently.

Figure 1 - A common emergent macrophyte in CSW
Figure 1 - A common emergent macrophyte in CSW

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Figure 2 - Minor herbivory on the macrophyte

Today (23 May), while wading though the wetland, I noticed that this plant has been hammered by herbivory (Figure 2 and 3). The nearly complete consumption of the leaves of this plant throughout the entire wetland appears to have been a result of a caterpillar (Figure 4 and 5).

  • What effects does this level of herbivory have on Thalia? Is it able to regrow leaves? Will it flower?
  • What is the herbivore? Is a a moth? Is a multivoltine and will it knock back the Thalia when it grows back? Why does it appear to specifically feed on Thalia and how to the adult find it?
  • Where are the pupa?
  • Where were the caterpillar predators to mediate the herbivory? The caterpillar seems rather conspicuous, so does it employ some sort of other prey escape mechanism, like tasting bad?

Figure 3 - Massive herbivory on the macrophyte from Figure 1.
Figure 3 - Massive herbivory on the macrophyte from Figure 1. Notice that there are limited reminents of the leaves on each stem or petiole.

Figure 3 - An active herbivorous caterpillar on the macrophyte from Figure 1
Figure 4 - An active herbivorous caterpillar on the macrophyte from Figure 1

Figure 4 - An active herbivorous caterpillar on the macrophyte from Figure 1
Figure 5 - An active herbivorous caterpillar on the macrophyte from Figure 1

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