Showing posts with label dawn. Show all posts
Showing posts with label dawn. Show all posts

Bull Ants Feed at Twilight

Bull ants do not feed during all daylight hours. Observation has shown that they feed at twilight. When the sun is brighter for longer for example in summer, or there is no cloud cover, bull ants forage for food later in the day. When the sun is darker, earlier, they search for food sooner in the day. It was believed that all insects fed according to circadian rhythms, but this does not seem to be the case.

Activity in the nest was affected by cloud cover. Outside activity that involves feeding occurs at twilight. Obviously, they are feeding during these short intervals to avoid predators: most animals that eat ants would be inactive at twilight.

Tests were done at ANU in Canberra. Bull ants were put in containers where diffused light was altered. It was found they only fed when the light was set at a particular low level. Evolution does take some winding paths. This shows though that evolution develops in a rational way.
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Entomology
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Asteroids Can Have Magnetic Fields

It has been found that asteroids can have magnetic fields. This was quite a surprise. Planets have magnetic fields due to a moving molten metal core. Mercury has a very strong field. The reason for this is not yet known.

Vesta is a large asteroid with a diameter of 525 kilometer. It was first identified in 1807 by Heinrich Wilheim Olbers. It is the most easily seen asteroid from Earth. Smaller asteroids hit Vesta and some of the debris falls to Earth. The fallen "rocks" can be linked to Vesta because they have the same spectral color match.

Vesta is unusual for an asteroid as it once had a crust, mantle and molten metal core. The orbiting dawn spacecraft/satellite confirms this. It is now frozen and no longer active. A meteor named Alan Hills A81001 composed of Vestan crust fell to Earth in the Arctic. When it was analysed it was found to have a weak magnetic field.  The original crust gained  a magnetic field when it cooled 3.7 billion years ago. An impact a billion years later hit the frozen crust. This melted and refroze some crust which resulted in magnetism being transferred, imprinted, on rock which became the Alan Hills meteor.
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Science
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Bull Ants Feed at Twilight

Bull ants do not feed during all daylight hours. Observation has shown that they feed at twilight. When the sun is brighter for longer, for example in summer or there is no cloud cover, they forage for food later in the day. When the sun is darker, earlier, they search for food sooner in the day. It was believed that all insects fed according to circadian rhythms, but this does not seem to be the case.

Activity in the nest was affected by cloud cover. But outside activity that involves feeding occurs at twilight. Obviously, they are feeding during these short intervals to avoid predators. Most animals that eat ants would be inactive at twilight.

Tests were done at ANU in Canberra. Bull ants were put in containers where diffused light was altered. It was found they only fed when the light was set at a particularly low level. Evolution does take some winding paths. This shows though that evolution develops in a rational way.
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