Ever look up at the stars and wonder if some bug-eyed creature is doing the same? It turns out at least one does: the dung beetle uses the glow of the Milky Way to navigate.
Once a beetle (Scarabaeus satyrus) has constructed its dung ball, it moves off in a straight line in order to escape from rival beetles as quickly as possible, lest they try and steal its carefully crafted ball. This behaviour doesn’t sound complicated, but several years ago, Marie Dacke of Lund University in Sweden and colleagues showed that polarised light from the moon is important for dung beetles to keep to a straight line.
Then the researchers were surprised to find the insects were able to stay on course even on a moonless night. “We thought there was something wrong in our set-up,” Dacke says.
The team allowed the beetles to crawl around the floor of a plain-walled cylindrical drum with an open top, meaning they could only use the night sky to orientate themselves. The researchers timed how long it took the beetles to reach the edge of the drum from the centre, and found that under a full moon, the insects took around 20 seconds on average; on a starry but moonless night, they took around 40 seconds.
But when beetles had a cardboard cap placed on them to prevent them from seeing the sky, they needed over two minutes, suggesting the stars were playing a role.
Important dung beetle news.
The garden ant and the cockroach wasp are just two new examples of insects acting as their own pharmacists—using self-made chemicals to defend themselves against bacteria. In the simplest strategies, they groom themselves with defensive chemicals. Ants and termites do this, as do rove beetles, which use a substance called stenusine to walk on water as well as repel fungi and bacteria.
Some species use their chemicals to clean their homes, relatives, or food supply. Some bees and wasps incorporate their venom into the building materials for their nests. Fire ants apply antibacterial chemicals onto their eggs, and liberally spray the stuff into the brood chambers, where the eggs are kept. The European beewolf—a type of parasitic wasp—embalms the honeybees that it provisions for its larvae, by covering them with an oily secretion that stops water from condensing and makes it harder for fungi to grow.
At a time when many human societies lack decent sanitation, and others have only enjoyed it for a few centuries, it’s sobering to remember that insects have been practicing careful hygiene for millions of years.
Important bug news.