Turtlehead flowers

Turtlehead flower (Chelone glabra) is one of my favorite native plants and I had to get one when I came across individuals for sale (Edge of the Woods has them in Oresville, PA).

When I was walking out to my truck I noticed a bumblebee visiting the plant and it disappeared! Then I noticed a leg sticking out. 

Two petals of the corolla close down like the jaws of an alligator. The bumblebee is large enough that it has the muscle to lift the top and crawl inside. This is just another mechanism that plants use to exclude some pollinators and increase the probability of having a narrower pool of pollinators. This increases the probability that pollen goes from turtlehead to turtlehead. Other mechanisms include corolla length (long corollas are pollinated by long tongued insects, colors, timing of flowering, and even deception). Cool stuff. 

There's a bumblebee in the front flower and you can see one of her black legs sticking out the left side 

Bee leaving