Bees and Baptisia

Seems to be wondering, “Just how do I get in here?”

Another reliable plant in our front garden is the perennial Blue False Indigo, Baptisia australis, a member of the family Fabaceae (legumes) that contains other garden plants such as beans, sweet peas, lupines and the shrubby caraganas. Blue False Indigo grows best in gritty well-drained soil, but it also does well our clay-based Edmonton earth. It can be slow to establish, but is long-lived and will eventually grow to about 90 to 120 cm tall (3 to 4 feet) and wide. The stems begin branching half-way up and have grey-green foliage with trifoliate leaves. The flower spikes are tipped with upright terminal racemes with the pale blue to deep violet pea-like, bisexual flowers about 2.5 cm (1 inch) long. It thrives in full sun and is tolerant of dry conditions.

At the doorway, but how to open it?

B. australis flowers in early summer for about two weeks. The sexual parts of the flowers are enclosed by the two lower petals (called a keel), with the pollen-bearing anthers in close contact with the stigma,  so it can be self-pollinating. However, the flower design still allows for insect pollination in a very selective way.

Ghostly anthers within the keel.

Ghostly anthers within the keel.

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Baptisia flower petal arrangement

The petals of the Blue False Indigo flower are arranged in a classic pea-flower shape. There is a large upper petal called the banner (sometimes called the standard) with a petal called the wing on either side. The two lower petals that form the keel are fused on the bottom edge and contain the stamens and pistil. The nectar lies at the base of the stamens, which are unreachable by most insects. Most, but not all–bees of a certain weight and/or persistence can find a way to get at the riches of nectar and pollen that are hidden deep within the flower.

Bombus nevadensis feeding at False Blue Indigo, Baptisia australis.

Big bee, no problem. This queen Bombus nevadensis uses her mid-legs to hold the wing petals and reveal an opening at the base of the flower to reach the nectar. The keel has opened to reveal the stamens which brush under her abdomen.

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The smaller leafcutter bees (Megachilidae) don’t have the weight, so they resort to a more forceful entry method…

...using its mega-jaws as a  brace,

Using its mega-jaws as a brace…

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…and pushing down on the wing petals, raises the anthers and the stigma to brush pollen under the bee’s belly. Note the wear-and-tear on the wing petals–this flower has been visited a few times before.

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Here’s another view, with a newer blossom and the bee pushing down the keel with the hind legs, exposing the green stigma and the yellow pollen-coated anthers. Did it reach the nectar?

And another view on an older flower. Enthsiastic waving of the abdome clearly show the pollen-gathering site on Megachile species is under the length of the abdomen and called the ‘scopa‘. The anthers, stigma and style are also clearly visible.

And another view of a Megachile on an older flower. Enthusiastic waving of the abdomen clearly shows the pollen-gathering scopa under the abdomen. The anthers, stigma and style are also clearly visible.

Another view, with the legs at work inside the keel. It appears that the legs are brushing pollen up to the scopa.

Another view, with the legs at work inside the keel. It appears that the legs are brushing pollen up to the scopa.

(All images taken in our front garden in Edmonton, Alberta between June 24 and July 3, 2014)

This entry was posted in Alberta, Canada, Documentary, Edmonton, Education, garden, Hymenoptera, Insect, macro, Megachilidae, photography, Pollination, Season, Summer and tagged , , , , , , , .

One Comment

  1. Charles Bird 31 March, 2015 at 6:33 AM #

    A fascinating series of photographs Adrian. Excellent photography, as usual. The interrelationships and dependencies between flowering plants and insects is almost mind-boggling.