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A wild plant took root in our garden. We decided to let it grow to see what it was. It turned out to be a Late-flowering Boneset Plant (Eupatorium serotinum), also known as Late-flowering Thoroughwort or just Late Boneset.  We immediately noticed that the plant was very fragrant and attracted quite a large number of pollinators. Below you can see a sampling of some of the pollinators that visited the plant. It seemed that all these pollinators were having a good time feasting on the nectar of our boneset plant and contributing to its reproduction. However, we then spotted a large bug feeding on a bee it had just caught. We were surprised at the structure with spokes in the back of the insect. What was this bug?  The bug turned out to a specimen of Arilus cristatus, the North American Wheel Bug. It is presumably called this because the spoke-laden structure in their backs reminds people of a wheel. The wheel bug is a type of the so-called assassin bugs which belong to the family Reduviidae. These bugs stab their prey with their very sharp proboscis and injects them with enzymes that dissolve the interior of their bodies, which they then proceed to drain.  But the wheel bug was not the only assassin lying in wait on our boneset plant. We also spotted a praying mantis lurking among the stems and leaves.  The mantis spotted a bee and moved with lightning speed upon the hapless insect, which became its meal.   So it seemed that our boneset plant could also be a death trap for some of our pollinators. The wheel bug and the mantis are both ambush predators. They frequent scented plants that attract their prey and lie in wait for the right time to attack. The drama of life and death in nature often unfolds right before our eyes, but we don’t notice it. And all it took was a fragrant plant in my garden to bring this reality to my attention. All photographs belong to the author and can only be used with permission.
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In the field of optics, a caustic is a set of rays of light that have been reflected or refracted by a curved surface and focused into another surface. The classic example of caustics or a network of caustics is the bands of light you get at the bottom of a pool when the light shines from above. The top of the waves crisscrossing the pool act like a convex lens concentrating light on a focal point. This is incidentally why they are called “caustics”, from the Greek “to burn”, as when sunlight is focused by a lens into a small area. If this focal point coincides with the bottom surface of the pool, the caustic band will be sharp, whereas if it doesn’t, the caustic band will be diffuse. On the other hand, the areas between the top of the waves have a concave shape and they act to disperse the light. This is why caustics are separated by areas that seem to be darker. In the video below, I have slowed down the network of caustics in a pool down to 240 frames per second. You can follow the caustic bands and see how they appear, disappear, merge, and separate continuously as a result of the pattern of waves on the surface of the water in the pool. |
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