Burrowing bees

Author
by Kate C
Publish date
18 December 2013
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No biologist worth their salt will stumble across a burrow in the ground without having a good stickybeak. And museum biologists are definitely worth their salt*.

So when the Alpine National Park Bioscan team found several hundred small burrows in one spot, they couldn't just wonder if they were made by crayfish or perhaps mole crickets. This hypothesis needed testing. Colin from Live Exhibits got to digging.

hut in the Alps Burrows in the foreground and Davies Plain Hut in the background.
Source: Museum Victoria
 

He stuck a blade of grass down the burrow and used a spoon to carefully dig around it. About 30 or 40 cm down he found, not a cray or cricket, but a little bee. It was no coincidence; a second excavation turned up another bee in the next burrow.

Colin digging holes Colin digging up burrows with a spoon.
Source: Museum Victoria
 

The bees belong to the subfamily Halictinae, which happens to be the speciality of museum entomologist and bioscan participant Dr Ken Walker. He collects most of his study specimens as they are out foraging and rarely sees the burrows. And he'd never seen burrows in such high density –about 400 in one small grassy area.

Ken explained that the bees belonging to the genus Lasioglossum and subgenus Parasphecodes. "Lasioglossum is one of the largest genera in Australia, doing most of the work of pollinating." These burrows are where the female bees brood the next generation.

Halictine bee The halictine bee responsible for the burrows.
Image: David Paul
Source: Museum Victoria
 

"They're a semi-social bee," said Ken. "In a single nest there can be six to ten females, which are all queens. They all lay their own eggs, and they all help excavate that main tunnel but each one of them then makes a lateral tunnel by themselves. At the end they build a group of cells each lined with saliva, and they put in a pollen ball mixed with a little bit of nectar, and they lay an egg and close the whole thing up."

But that's not the end of the story, because the bee larva isn't alone in the cell. Looking closely, Ken spotted a number of large mites on the backs of the bees. The mites are harmless to the bee since they're a non-feeding, migratory (or hypopial) life stage, waiting patiently for the bee to finish stocking the brood cell with pollen.

Halictine bee with mite The red arrow shows the location of a hitch-hiking mite on this bee.
Image: Ken Walker
Source: Museum Victoria

Mite on a bee Detail of a mite on the back of a bee.
Image: Ken Walker
Source: Museum Victoria
 

Said Ken, "just before the bee closes up the cell, she turns around and brushes one or two mites off, which then develop to the feeding and sexual stages." The mites act like little housekeepers, eating any mould or fungus that attacks the pollen ball and thus keeping it fresh for the developing bee. When the new adult bee is ready to emerge, the mites' own young clamber aboard and travel on to the next burrow. "It's a wonderful relationship there."

Halictine bee Dorsal view of the burrowing semi-social bee.
Image: David Paul
Source: Museum Victoria
 

So there you have it – nosy biologists reveal an underground community of fascinating little animals, and Parks Victoria rangers have an interesting reason to recommend that tents be pitched away from the field of muddy burrows.

*Humans contain about 0.4% salt by weight. So a 70kg museum biologist, say, contains about 280g salt**. That much table salt costs about a dollar from a supermarket. If instead we say they're worth their weight in gold, according to today's price, and the Dynamic Earth scale, that puts our 70kg biologist at $3,112,900. The real value is probably somewhere in the middle.

**Except marine biologists. They're a bit saltier.

Links:

ABC Bush Telegraph: Hive of activity reveals all in alpine bioscan

The Age: Critter census reaps bonanza for researchers

MV Blog: Alpine Bioscan

Comments (2)

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Ella B. 18 December, 2013 17:20
What a fascinating web of life story! How many of them still has not been discovered? Thank you Kate!
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Jethro 19 December, 2013 22:02
As one of the local Rangers I will be advising people don't camp in this area as I know that there is a whole world underneath of bee homes that I can explain to visitors. Thanks MV
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