Onosmodium Insects

The larvae I was monitoring in the False Gromwell flowers have disappeared.  This doesn’t surprise me, because it is the normal conclusion whenever I try to follow caterpillar development in the wild.  Larvae often move to new parts of the plant as they grow and some even move to new plants, so there’s a chance they are alive and well in a different location.  They may have represented some small species and have already pupated.  I suspect they may have been eaten.  If I was able to find them, they should have been easy to discover by some caterpillar predator.

Those larvae may be gone, but something has deposited a bunch of new eggs in the flower whorls.  Maybe these are from the Onosmodium moth I’ve been looking for.

The Onosmodium plants are performing exceptionally well this year.  Many may top four feet once their flower stalks have completely extended.  While searching for my missing larvae, I took the time to examine a few other residents of the Onosmodium plant.

Some insects are found on a plant because of developmental requirements that can only be satisfied by a particular plant species.  Other insects are there just because the plant is a convenient resting place.  The host plant for this Elegant Grass-Veneer moth is grass, which is found in abundance in the prairie areas in which the Onosmodium grows.  To be fair, I have to admit that these moths were so abundant that they were probably resting on every plant in the area.  I couldn’t move without causing a few to take flight.

Small, black beetles were on all of the Onosmodium plants.  Most were doing like this fellow and struggling to negotiate the hairy stalks. 

Fireflies are another insect that just use the plant as a convenient resting structure.  Here is a Photinus species displaying one of the more comical insect faces.  This is a common species responsible for much of the low level flashing seen on summer evenings.

Bumblebees are common visitors to Onosmodium flowers.  Most were carrying impressive masses of pollen.  I often see bumblebees spend the night on nectar plants, so I’m not sure how often they actually return to the nest or how long it has taken to accumulate all of that pollen.

Southern Cloudy Wings were frequent visitors to the Onosmodium flowers.  Most nectar gathering insects tend to concentrate on a single plant species that offers an abundance of flowers.  When blooms fade on that plant species, the insect will begin visiting the next most abundant nectar source.  This habit benefits the plant by increasing the odds that flower visitors will be carrying the right pollen for that plant. The Southern Cloudy Wings consistently passed by other nectar producing species in order to reach the next patch of Onosmodium.

I found many insects in early developmental stages.  The best I could do in identifying this fellow was to determine it to be some type of Hemiptera that is not an aphid.  It was fairly fast moving and continued to evade my observation.

Small flies were particularly abundant on the Onosmodium.  This Rivellia species systematically traveled the plant leaf-by-leaf until I inadvertently scared it off.  It rarely paused and I have no idea what the object of the search may have been.

These two flies were doing a dance on the flower’s exerted style.  One fly would shift its body to one side and the other would match the maneuver.  The body shifts continued for a while and then one fly took off.  As with so many things I observe, I can’t explain the why behind the behavior, but that doesn’t make it any less fun to watch.

Onosmodium and Larva

There are certain caterpillars that I see each year, but by the time they become noticeable, they’re of a fairly large size.  I’m making an effort to see some of these at their earliest stage of development, so I can get an idea of their life history.  A good example is the caterpillar I find on the False Gromwell, Onosmodium molle var. hispidissimum, in late summer.  I’ve never seen the earlier larval stages.  I don’t even know its species.  I just call it the Onosmodium moth.  I have run into people who know this moth and they call it the "Oh yeah.  I know that, but I can't think of the name."

I’ve been watching the Onosmodium since it emerged and have recently noticed some signs of leaf feeding.  The damage was concentrated in the area of new leaves at the top of the plant.

By folding back the developing leaves, I was able to trace the evidence of feeding right down to the emerging flower buds at the center of leaf formation.  Damage on the old leaves matched that of the newer leaves, so the feeding probably happened when the leaves were young and closely wrapped.

As I folded back the final leaf, I discovered this small larva at the heart of the new growth.  This part of the plant will soon unfurl into a long stalk of flowers.  I’ve noticed in the past that the larvae begin feeding on the flower stalk and later move down to the stem leaves.

I don’t know yet if this is the same species of larva that I’ve seen in the past.  I’ll keep watching its progress.  No matter what it is, I’m sure that I’ll learn something of interest through frequent observation.

Onosmodium was an uncommon plant at Blue Jay Barrens when I began my management activities.  It forms a large seed that is easily stripped from the plant, so I began collecting the seed and scattering it around the immediate area of the plants.  Areas along trails got the most attention and this Onosmodium patch near the trail head has grown from a few plants to several hundred.  There’s plenty of food here for the Onosmodium moth.

Prairie Garden - Mid June

June is when the prairie garden goes through the green weedy stage. Of course I don’t consider it weedy. I call it that because now is when I’m frequently asked why I don’t mow that patch of weeds in the middle of the yard. The most noticeable feature at the moment is the Prairie False Indigo, Baptisia lactea. This tall perennial legume dominates everything, at least as far as height is concerned.

Prairie False Indigo begins growth in the late spring and suddenly shoots up tall spikes that produce creamy white flowers. A healthy plant can reach 6 feet or a little better. The pea-like flowers are attached singly to the central stalk. Leaves develop more slowly, but become an impressive display themselves later in the season. Leaf height is typically half that of the full plant.

It won’t be long before the prairie garden becomes more colorful. Butterflyweed isn’t a common plant in the more established prairies of Blue Jay Barrens, but I scattered a few seeds here to make this project a little more palatable to the uninformed public.

There may not be a lot of color, but the prairie garden is full of interesting plant features. The False Gromwell flower stalks are beginning to unfurl. The curled stalk straightens a little bit with each flower that matures. The entire stalk will be held up straight by the time the seeds are ripe.

Dwarf Plantain, Plantago virginica, is one of those plants that needs open soil in which to grow. Being an annual means that this plantain must produce a good crop of seed in order to guarantee a population next year. It’s odd that the species is so rare here, since there are so many areas of bare ground. Populations don’t seem to last for more than a few years in any one spot before dieing out. The frequency of the plant seems to stay relatively constant, but the locations keep changing.

Except for the absence of dead plant material from last year, you wouldn’t know that this area had been burned in the spring. When left unburned, the old plant residue disappears through the course of the summer as it’s consumed by soil organisms. I wonder how much the soil biota suffers when we deprive them of this organic feast.

The prairie grasses are putting on some rapid growth this spring. Excessive rainfall and above average temperatures seem to really encourage the growth of this Sideoats Gramma.

The Spider Milkweed has managed to produce one seed pod. The Milkweed Bugs are already probing for a taste of the developing seeds.

Another of the uncommon milkweeds, Green Milkweed, Asclepias viridiflora, is preparing to bloom. This is a rather inconspicuous species that only shares its charms with those who are willing to get their eyes up close.

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.

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.