Monday, August 10, 2009

Onosmodium Moth Larva

There is a larva that feeds on the False Gromwell, Onosmodium molle var. hispidissimum. It’s an attractive larva, with a golden head and four gold bands around a black velvet body. I don’t know what it becomes.

Normally the larva will stay within a network of web tunnels built on the stem and leaves of the plant. Within these tunnels it can feed and is protected from many predators. I don’t know why this individual has decided to run about.

The plant takes on a ragged appearance after awhile, but it doesn’t seem to suffer any life threatening damage. I’ve tried rearing a couple of these larvae in caged conditions, but have never had any luck getting an adult. A pupa was developed once and it looked very much like you could expect a moth to emerge. I have searched through this webbing in the fall and have found neither pupae nor their skins. I wonder if the larvae leave the plant and pupate elsewhere. This particular larva may be preparing for that journey.

You can keep track of feeding activity by cleaning the leaves and then watching for new droppings.

This larva didn’t seem to be moving inside its web tunnel. It may be molting or pupating or dead. I’ll try to check later and see what has happened.

The seeds develop satisfactorily even when covered by webbing. The webbing does seem to hinder seed dispersal somewhat. You’ll often see the entire top of the plant fall off as one unit neatly bound by webbing.

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