random bee: Exomalopsis - leg warmers & deep digs

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A note on random bee:

This is the sixth genera of bees we have covered so far, and with about 425 bee genera existing total (the actual number is debatable), that means we have covered 1.4% of all bees known! Yippee!

If I cover three genera every week, then it would only take just over three years before we discuss all of them - better lock in! (holy shit that's a lot of bees).

If I cover only one genus every week, it would take just over 8 YEARS to cover all of them (does that help explain how many bees there are?).

And remember we are discussing genera, not even individual species. If I covered one species of bee every day, it would take over 54 years to hit them all :). Terrifying.

Today's random bee is:

Genus: Exomalopsis

Family: Apidae

Subfamily: Eucerinae

Tribe: Exomalopsini

Exomalopsis is only found in the Americas, including across most of the US, all of Mexico, and the majority of South America. There are 88 species in the genus and they live in a diversity of habitat types, including arid deserts and rain forests.

Some are fairly colorful with pale or orange hairs and green or gray eyes. Like most Apidae bees, the females have long pollen collecting hairs on the back legs called scopa, and the scopa are especially long and fluffy in this group. It looks like they are wearing 80s leg warmers. As in common in males, the antennae are very long and sometimes their mandibles are yellow.

Exomalopsis is apparently Greek for "not bad looking"?? Who is shaming these bees?? They're really beautiful (even by conventional standards).

This group and a sister genus, Anthrophorula, have a distinct characteristic to identify them. They have a row of upright well-separated hairs lining the inner side of each eye. It's like they have a short fringe around the inner eye.

This genus builds underground communal nests, where several individuals share the nest entrance and build their own chambers off of that entrance. They build some of the deepest bee nests ever recorded, including one 16 feet (5 meters) deep in Brazil! Most of them are not that deep, though. There is usually one main tunnel that goes downward, then several branches lead off to cells where the eggs are laid. 

Some Exomalopsis in California will nest in the walls of claylike soils, using the cracks in the soil as entrypoints. Like all solitary bees, females create a pollen-ball provision for each individual egg, which the larvae feeds on when the egg hatches. In this case, the provision is more loaf-shaped and has a little 'foot', a raised area at one end that allows air flow underneath the loaf, possibly to prevent it from getting too wet or damp. Bee nests suffer from a lot of moisture issues, especially bacterial and fungal growth, so controlling that is a big aspect of a lot of nesting behavior.

Exomalopsis are mostly diet generalists and visit lots of different flowers. Apparently they can also 'buzz pollinate', which I thought was a feature only in bumble bees. It's when the bee holds onto a flower and vibrates its body very rapidly, which is required in some flowers to actually loosen the pollen grains from the anther. Some plants like tomatoes can only be pollinated this way.

Many Exomalopsis are associated with kleptoparasites, or nest-stealing bees, including cuckoo bees.