A new experiment has shed light on how the monarch butterfly executes its impressive 2,000-mile migration every fall, and all it took was a lick of paint.
Researchers already knew that the butterflies use the sun to guide them to the exact same wintering spot in central Mexico. But because the sun is a moving target, changing position throughout the day, biologists have long speculated that in addition to having a “sun compass” in their brains, butterflies must use some kind of 24-hour clock to guide their migration [Wired.com]. In a new study, published in Science, researchers determined that the butterflies have a second circadian clock in their antennae, which sense light.
The researchers conducted the test by holding the butterfly wings gently and dipping their antennas in enamel paint. The ones with black paint were unable to orient to the south, they found, while butterflies whose antennas were coated with clear paint had no trouble navigating [AP]. This proved that the antennae had to be able to sense light for the butterflies’ navigation system to operate, and also showed that the butterflies weren’t navigating by scent, as both kinds of paint interfered with the insects‘ sense of smell.
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DISCOVER: The Flight of the Butterfly
Image: Monarch Watch / Chip Taylor
In a rare conservation success, a beautiful butterfly species that was headed for extinction has been brought back from the brink, thanks to careful biological observations of the insect’s life cycle. The mysterious disappearance of the Large Blue Butterfly across most of northern Europe was originally put down to its popularity among insect collectors [Telegraph]. Then biologist Jeremy Thomas spent six summers in the 1970s studying the very last colony of large blue butterflies in the United Kingdom, and determined that the butterflies were dependent on one species of red ant for their survival–and those ants were losing their habitat.
The butterflies lay their eggs on flowering thyme plants, and the hatched caterpillars fall to the ground and begin to impersonate immature red ants. They secrete chemicals and even make noises that make the red ants believe they are wayward grubs. The ants then mistakenly carry the caterpillars to their underground homes and keep looking after them even though the adopted intruders gobble ant grubs for 10 months before forming a chrysalis and flying away as adult butterflies [Reuters].
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A species of European butterfly has an excellent trick for protecting itself during a vulnerable stage of life. As the caterpillars prepare to enter their inactive pupal stage they emit ant-like chemicals that cause red ants to scoop them up and bring them inside the ant colony. Then, to get star treatment, the caterpillars make a rhythmic noise that resembles the call of the ant queen. That’s enough to get the worker ants’ undivided attention, a new study shows. “They appeared to be treating the caterpillars as if they were the holiest of holiest, the pinnacle of power, the queen ant” [New Scientist], says lead researcher Jeremy Thomas.
If the colony is attacked, the worker ants save the caterpillar before they save ant larvae, and when food is scarce the ants have been known to kill their own larvae and feed them to the deceitful interlopers. But there’s one ant who is not fooled. Researchers set up an experiment in which a butterfly pupa pretending to be an ant queen was placed in a chamber with worker ants and four real ant queens. The ant queens began to attack and bite the caterpillar, but the workers intervened, biting and stinging their own queens, which they then pulled to a far corner of the chamber while other workers attended the pupa [AP]. Researchers note that this situation would not arise in the wild, where queens and larvae inhabit different chambers, but say it shows where the workers’ loyalty lies.
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