Monday, June 18, 2012

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.

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