More Evidence of Potential Animal Pollination In some Grasses

Purple stigma on the upper left of the hoverfly, as it looks around for yellow anthers

In previous posts, the topic of animal pollination of grasses was discussed.

Life without Animal Pollinators: Why Grasses Embraced the Wind

Bee mimicking fly on flowers of Phalaris arundinacea cultivar

I was looking at what I thought to be a small specimen of Andropogon sp. here near Boulder, Colorado, when I noticed that many small insects were landing on the flowerhead and spending time perusing through the yellow anthers.

The insects that buzzed and crawled among the yellow anthers and purple stigma seemed to all be hoverflies, similar to those that I had seen frequenting the flowerheads of Phalaris arundinaea in New Jersey. 

Hoverfly eyes a good meal

As I noted in the previous posts, the insects seem to eat the pollen directly using its extended proboscis, and this could facilitate pollination when pollen sticks to it and transfers to a stigma during its visit to another flower.

Like all grasses, A. gerardii relies on wind pollination for the dispersal of its pollen, and the reason behind its lack of dependence on animals is discussed elsewhere. But it would not make sense to turn down the services of insects and other animals when they could enhance delivery, and this is perhaps what is happening in this case.

Interestingly enough, there have been reports of other insects such as bees also rummaging among grass flowerheads, but I have yet to see such cases.