The Leafcutter Bee: The Can Opener of the Bee World. Megachile sp.

If you happen to notice some beautifully cut, circular holes in your rose leaves you may well have some Megachile bees in your garden.

There will be no great damage to your plants and what some may find unsightly, I think is rather attractive.

Also, when you know that the female Megachile is just using the leaves to wrap her little ones in, you would hardly begrudge her a leaf or two, would you?

To help her this little bee is equipped with very strong chewing mandibles which she uses to bite through the leaves. It only takes one or two seconds for her to complete this operation.

Here is a sequence of photos by different photgraphers from the excellent photographic site Arkive: Images of Life on Earth, and the text is from “Bees of the World” by Christopher O’Toole and Anthony Raw.

Round-notches-cut-from-rose-leaves-by-megachile-leaf-cutter-bees

“Just before the leaf fragment becomes completely detached the female vibrates her wings rapidly so she is already in flight as soon as the leaf is free.
She then flies a short distance and lands on the ground, a stone or a tree trunk while she adjusts her load. If the leaf fragment is longer than broad she uses her feet to fold it lengthways, so she straddles the leaf with its convex surface towards her. She flies back to the nest carrying the leaf in this way.”

 

Megachile-leaf-cutter-bee-transporting-leaf-in-flight

There she makes beautifully crafted overlapping nest pockets, a kind of natural origami pot with which she lines her nest.

She sticks the leaf fragment together by crimping the edges of the leaves so that sap oozes out and this possibly with salivary glue acts as an adhesive.”

Megachile-leaf-cutter-bee-nest-of-sticked-and-rolled-leaves

I am fascinated by the shape. These individual cells must fit into each other so the bee must know to taper them.
Here is a very nice description from an article by Louise Kulzer from the website;

Bugs of the Month” by Scarabs: The Bug Society, here

Actually, it’s a bit more elaborate than just lining the nest burrow. Leaf-cutter bees construct several cells from the leaf pieces they collect. The cells are positioned end to end in a long burrow.
Several circular leaf pieces form the bottom, then oblong pieces are placed along the sides to form a “thimble.” This thimble is then provisioned with nectar and pollen, and an egg is laid in it.

Then the bee cuts more circular pieces to close the cell. Once the cell is closed, the bee starts another cell above the first, until the whole cavity is filled. Like all solitary bees, the female leaves the nest after it is closed. The grubs fend for themselves on the nectar and pollen.

The adult leaf-cutter bee is smaller than a honey bee, dark, often hairy, with a prominent pollen basket below. Females are workaholics, and are a delight to watch because, being so intent on cutting leaves, they usually ignore a nearby observer!
The leaf sections are cut with the mandibles, and the bee forms an arc with her head along the leaf edge to make the circular shape. (They remind me a little of an electric can opener, only with much more personality.)

The facts
CLASS: Insecta
ORDER: Hymenoptera, Bees, wasps, ants and sawflies.
SUPERFAMILY: Apoidea. Bees and some wasps.
FAMILY: Megachilidae
GENUS: Megachile

The Megachilae are a huge genus of bee with well over 500 species. The most important North America species is the Alfalfa leafcutter bee Megachile rotundata which is used for alfalfa pollination.
A monster member of this family is Megachile pluto. A female can reach 1.5 inches long.

Stavenn_Megachile_pluto

photo by Stavenn from Wikipedia here.

My bee is Megachile brevis a delightfully smart and perky little bee. The body shape is unusual in that there is a definite upward tilt rather than the more downward curved body shape of other bees.
These bees, like all of the female Megachile species carry dry pollen under their abdomen in the stiff bristly hairs called the “scopa” which in other bees is located on the legs.
I have Sam Droege and Anna to thank again for their help.

There was only one way I wanted to draw this bee. She had to show her stripes and pointed abdomen and the pollen basket, so a side view to show the tilted body shape too.

megachile sketch

A friend of mine described her yesterday as “very sassy”!

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Bee number 15: The Leafcutter Bee, Megachile brevis


megachile leafcutter bee

Watercolour on Arches HP, Image size 3.5 inches.

BOB, The Gentle Blue Orchard Mason Bee : Osmia lignaria

The headline that first caught my eye when I started reading about these bees, says it all.. “This Bee Is Gentle” … A fact that is reiterated again and again, here is a quote from “The New Mexico Native Bee Pollinator Project” calling on gardeners in NM to help make “bee corridors”;

“Gardens for the more flamboyant hummingbirds and butterflies have become popular; now the bees need our support. There’s a fear factor with bees however, even among nature lovers.
Honey bees sting because they have a treasure trove to defend, and a queen who lays all of the eggs. Not so with native species: the vast majority of them are solitary bees who ARE VERY DOCILE and do not sting unless they are handled roughly.

When we become educated about our bees, a new understanding develops that they can be both safe and a delight to have around.”

This comes from the USA site Pollinator Paradise which has as much information about Blue Orchard Mason bees and other helpful native bees as you could ever wish for. It is run by Dr Karen Strickler who I have to thank for information, samples and pointing me in the right direction for my research on these bees.
Orchard bees have many champions and I have been amazed by how many suppliers are selling mason bee items, you can buy mason bee homes, which come in many different varieties from high rise blocks to bundles of straws; you can buy mason bee videos, mason bee online courses, and of course the bees themselves which come as little cocoons with full owners manuals.

Blue orchard bees overwinter as dormant adults so you can watch them emerge in the spring ready to start work, For a comprehensive listing of suppliers of everything, go to Pollinator Paradise here. You will be there for hours..!

So why all the fuss? Well this little bee is an ace pollinator of fruit crops and again, in face of the honey bee decline, the native bees are coming into their own.
If you have a small domestic orchard.. apples, cherries and other tree fruit just 50 blue orchard bees will help secure you a good crop.
(These bees are endearingly referred to as “BOBs” by the US Dept of Agriculture and there is a good article about them plus their possible predators here.)

Osmia_Apple9

BOB, on apple blossom from Karen Strickland at Pollinator Paradise

Minor mining

Although these are “solitary” bees, with each female making her own independent nest, they are gregarious and like to nest close to each other. They are opportunist nesters and will use old insect holes in wood, nail holes, and spaces in crumbling mortar.
They are not destructive as often thought as they do not burrow into mortar, but just make do!

Their name mason bee comes more from the fact that they seal their nests with mud.. so they make rather than destroy. They also like old hollow canes and can have as many twenty nest cells in one cane. J

ean-Henri Fabre, who I mentioned in the last post had hoped to find some Osmia nesting in the upright hollow reeds used by gardeners and farmers for fencing and supports…..from “Bramble Bees and Others” 1915:

I have often explored them in the hope of finding Osmia-nests. My search has very seldom succeeded. The failure is easily explained. The partitions and the closing-plug are made, as we have seen, of a sort of mud which water instantly reduces to pap.
With the upright position of the reeds, the stopper of the opening would receive the rain and would become diluted; the ceilings of the storeys would fall in and the family would perish by drowning.

Therefore the Osmia, who knew of these drawbacks before I did, refuses the reeds when they are placed perpendicularly.

 

Smart these bees..!

diagram nest

Drawing by Mike Kridle from Pollinator Paradise here

 

The Orderly Queuing of Bees.. with just a bit of nipping and shoving.

The tubular nests are fascinating and it seems that the size of the bee may depend somewhat on the size of the tube. The bee painstakingly makes each cell, bringing pollen and honey to each, lays her egg, seals the cell with mud, then moves on.
The lava will eat the provisions, spin a silk cocoon and stay in this safe house until the spring. In a way that is still not understood the lava knows which way to face before it spins the cocoon, facing backwards would be a disaster as there is only one way out.
I detected a problem here… if the first bee at the back of the nest develops first how does it get out when its younger siblings are still in their cocoons?

“Bees of the World” by Christopher O ‘Toole and Anthony Raw explains:

“Because of the linear arrangement of the cells ..the youngest bee emerges first, followed by the progressively older bees. However as may be expected the oldest bees in the deepest cells often awake from their winter dormancy first.

An older bee is thus likely to meet with a still dormant bee in the next cell between it and the nest entrance.The problem is solved as follows: when the bee has bitten through the partition into the rear of the next cell it bites its way through the cocoon of the bee in front.
If the occupant is inactive the bee nips the rear of its abdomen. This awakens the second bee which begins to vibrate its wings.. Nipping is repeated if necessary until the bee nearest the entrance starts to bite its way through the nest enclosure
.”

This is an empty cocoon which Karen Strickler kindly sent me.
It is a beautiful translucent thing, light but very strong and fibrous.. just 1/2inch long

.cocoon

It occurs to me that Orchard bee cocoons complete with housing would make a wonderful Xmas gift for the keen gardener and nature loving child.. and me… (taps Chris on shoulder!)

If you in the UK there is lots of advice in the Nigel Jones’s excellent “Solitary Bees” pages here. (interestingly Nigel appears to be a cat)

Bee Friendly Gardens

Dr Strickler has some good advice for creating a bee friendly garden here.
Attracting these little bees is more about getting the right flowers at the right time, as they are most active between April and July.

Bob sketches

This is a pretty bee, and another challenge as she is a shiny blue/black but also quite a hairy little creature. This is the female. The smaller male has a rather fetching moustache and longer antennae. I am saving him for later.

 

sketch

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Bee number 14: Osmia lignaria, the very dainty Blue Orchard Bee


osmia lignaria blue orchard mason bee

Watercolour on Arches 300 HP, image 3.5”