I took a quick walk through one of our restored wetlands last week. Most plants had finished blooming for the year, but in some recently-mowed patches, there were some scattered flowers of beggarticks (Bidens sp) and blue lobelia (Lobelia siphilitica). I knelt down to look more closely at some small bees I spotted crawling around on the lobelia flowers.
I saw one bee crawl in and out of one of the flowers, but for the most part, the bees (and a few flies) were all hanging around at the base of the flowers. As I watched, I saw one slide its long tongue into the flower. I couldn’t tell if it opened up a hole or just took advantage of one that was already there. Either way, it was apparently “stealing” nectar from the flower through a back window rather than entering politely through the front door.
A bee inserts its tongue into the base of a lobelia flower while two flies loiter nearby.
Another bee stealing nectar.
I sent photos and questions to both Jennifer Hopwood and Mike Arduser, who are always generous about sharing their expertise with me. They both agreed with my interpretation, and Mike added some additional information. He said that blue lobelia flowers have slits in them that make this kind of nectar robbing pretty easy for bees.
It seems an odd strategy for a flower to make it easy for bees to steal nectar without providing any pollination services in return. Maybe the slits serve another purpose and the benefits outweigh the costs. Or maybe it’s just a random loophole that natural selection hasn’t yet closed. Regardless, blue lobelia plants tend to produce copious amounts of seed, so the flowers must get enough front door visitors to do the job.
In addition to the bees, there were a lot of flies hanging around the flowers too. Flies have pretty short tongues, and it didn’t look like any of them were sticking those tongues into the flower slits. Instead, they seemed to be feeding on the outside surface of the flower. Maybe nectar was seeping through those flower slits? Or maybe the bees were a little sloppy with their drinking and the bees were cleaning up after them? Whatever the reason, I saw at least as many flies as bees on the flowers, so there must have been some attraction.
Flies were crawling around the bases of the flowers too, apparently feeding on the leftovers.
I wish now that I’d spent more time examining the flowers, and that I’d brought one home with me so I could look at the slits under a scope. However, I hadn’t really planned to stop at the wetland, let alone to kneel down in the mud to look at bees stealing nectar from hapless flowers. Also, my neck was starting to throb a little from holding my head at an uncomfortable angle necessary to photograph the bees. Instead of sticking around to learn more, I took my camera, my muddy jeans, and my sore neck back to the truck and headed home.
Little cheater…
The Prairie Ecologist 
Hi Chris: I’ve seen bumblebees employing this strategy on morning glory blossoms that had closed for the day. They would land on the blossoms, head towards the base of the flower and cut through the petals to reach the nectar.
I’ve been enjoying your posts for some time now.
Best,
Bruce
The beekeepers I follow talk about this nectar-robbing behavior from time to time. I’ve never seen a bee cut into a flower, but it sounds as though they’re rather clever about it. I didn’t know about the lobelia slits; that’s an interesting detail.
This is interesting and reminds me of the alfalfa flower. My father was a farmer near Daykin, Nebraska and kept bees. Alfalfa is typically used as a hay crop with the best quality hay if it is cut at the start of bloom. Thus the bees do not get much of a chance to work the flowers unless the hay harvest is delayed or if the alfalfa is grown for seed. An un-worked alfalfa flower is closed, but internal access becomes possible by tripping the flower’s pistol. It takes a large or strong pollinator to do that easily. A honey bee can with difficulty, but will get bopped by the spring loaded flower mechanism. Dad claimed that the bees were irate and hard to work with if they were gathering alfalfa honey. Some observers indicated that the bees would bite a hole in the flower and raid the nectar that way. Anyway honeybees are not the pollinators of choice for alfalfa seed production. I have kept bees here in Illinois with the highest population and most production in the 80s when Ronny was president and the agriculture policy was diverted acres. It was necessary to keep the land weed free and not produce anything of value. The farmers all planted alfalfa, could not harvest the hay or seed. Most left it grow until flowering was nearly done, but seed was not mature. There was enough alfalfa in the area and the cutting times varied enough so that there was alfalfa blooming all summer. There was a summer long honey flow. I never noticed any cranky behavior of the bees, so could not conclude anything about their response to getting bonked with flower parts. When you get the chance, take a toothpick and play with the mechanism on an alfalfa flower. See what the pollinators have to put up with. From: The Prairie Ecologist To: phn1939@frontier.com Sent: Tuesday, October 10, 2017 7:54 PM Subject: [New post] Back Door Thieves #yiv8838667828 a:hover {color:red;}#yiv8838667828 a {text-decoration:none;color:#0088cc;}#yiv8838667828 a.yiv8838667828primaryactionlink:link, #yiv8838667828 a.yiv8838667828primaryactionlink:visited {background-color:#2585B2;color:#fff;}#yiv8838667828 a.yiv8838667828primaryactionlink:hover, #yiv8838667828 a.yiv8838667828primaryactionlink:active {background-color:#11729E;color:#fff;}#yiv8838667828 WordPress.com | Chris Helzer posted: “I took a quick walk through one of our restored wetlands last week. Most plants had finished blooming for the year, but in some recently-mowed patches, there were some scattered flowers of beggarticks (Bidens sp) and blue lobelia (Lobelia siphilitica). I” | |
I have pictures of bumble bees going into the base of obediant plant blossoms, as well as hummingbirds piercing sideways into the base of cardinal flower blossoms (as well as nectaring the conventional way). We call them nectar robbers. It does seem like it would take less energy to get nectar that way.
I was going to comment about honey bees and alfalfa but phn1939 beat me to most of it. What I want to add is that honey bees learn to avoid being hit by the trigger mechanism after a few times and discover a slit on the side of the flower from which they can steal nectar. They even learn from other honey bees how to do it. This is why honey bees are such poor pollinators of alfalfa.
http://pollinators.blogspot.com/2009/12/pollinators-robbers-and-thieves.html
http://pollinators.blogspot.com/2009/08/partners-and-robbers.html
Hi Chris, I want you to know that people like me who grew up on the prairie, and are now separated from it, really appreciate those muddy jeans and your sore neck. I now feel more connected to that prairie that I called home. Tromp on! Tromp on! Thank you from a Kimball, Nebraska girl (now grandmother).
thank you Jeanne!
Bees are so clever. Years ago in a prairie in Payne County, OK I witnessed a bumble bee slicing open the flower of Penstemon oklahomensis so it could get at the stamens. It was too big to fit inside the narrow corolla. Fascinating.
That is such a cool observation! Thanks for sharing.
Delightful!!! As always. :)
I was taking a look at that small black fly perched above the bee in pictures 1 and 2 (esp #2) and was wondering whether it was actually a predatory species because its mouth parts look like they would be used for piercing rather than dabbing. Could it be a bee? Curious whether this is true or not.
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