Sunday, August 1, 2010

Onosmodium Insects

At this time of year, I become most curious about the identity of this particular insect. I’ve mentioned this larva before. It feeds on the False Gromwell, Onosmodium molle var. hispidissimum, and travels through web tubes that it constructs on the plant. I’ve never found anything laying eggs on the plant. The larva apparently leaves the plant to pupate, since I’ve never found pupae or pupal skins in the web tunnels. Larvae raised indoors will pupate on the plant, but I’ve had no luck producing adults from the pupae. Netting the wild plants has only resulted in dead larvae in the bottom of the net. I suspect the wild larvae may pupate on or in the ground. I’ve raised False Gromwell in pots with the thought that I could cage the entire pot once larvae appeared on the plant, but none of my potted plants has ever hosted larvae. I’d really like to see an adult.

Whatever this thing is, it must be fairly common. Typically 60 to 70 percent of the plants are infested with larvae. A single plant may contain a half dozen larvae. I’ve cut a flower pot in half and plan to enclose the base of a plant containing larvae. With the pot filled with soil and the plant completely netted, I may capture a pupa. We’ll see what happens.

The frass from feeding larvae covers the lower leaves. Lower leaves are not consumed by larvae, but they never seem to remain healthy. While examining this plant, I found another neat little insect.

I believe this to be a nymph of the Spiny Assassin Bug, Sinea spinipes. There are a couple of similar species that can be readily separated as adults, but the nymphal descriptions made it difficult to be certain. There’s no doubt of it being an interesting little creature.

This clump of Gromwell was consumed by larvae the past two years. This year the leaves are blemish free. Feeding damage occurs late in the season and the loss of leaves doesn’t appear to hurt the plant or reduce seed production. Finding the adult form of this larva may be one of those things that’s going to have to wait until I have time to stay with the plant and catalogue visitors.


  1. Just found your blog Via gardeningangel.

    I love Day of the Triffids! I read that book earlier this year and watched the somewhat groovy movie. Good stuff.

    Cool insects. I will be sure to check back to see more!

  2. Hi, Rosey. Thanks for visiting. I don't run into very many Triffids fans.