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These bumblebees live on my balcony, in ventilation holes in doors and windows. I'm trying to find the exact name of the species, but I can't find any that look exactly like this. Their top segment is completely black and the bottom one is completely orange. I'm not 100% sure that these are bumblebees, but they behave like bumblebees, I mean, they fly horizontally and like nectar.

The location is in the southern part of Germany (Bavaria). The insects are ~20mm long, similar to the size of a honey bee.

enter image description here enter image description here enter image description here

The closest match is probably Bombus lapidarius, but Bombus lapidarius only have orange "tails", most of their bottom half is black.

It looks very similar or even identical to Bombus alpinus, but the problem here is that Bombus alpinus usually live in the mountains (and I'm in 300km from the closest mountains) and they are considered to be almost extinct in Germany.

Do you have any idea what they are called?

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  • $\begingroup$ Welcome to Biology.SE! When you wrote "south of Germany" I'm guessing you mean in the southern part of Germany (what you wrote means somewhere to the south of Germany — i.e. could be Austria, Switzerland, Litchenstein, Italy ..). On this assumption I've made a minor edit to your post. Please also edit in the size of these insects since that can be essential to their identification. ——— Thanks! $\endgroup$ – tyersome Mar 25 at 19:00
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    $\begingroup$ @tyersome Yes, I meant the southern part of Germany (Bavaria). Thank you for the edit! $\endgroup$ – lawful_neutral Mar 25 at 19:29
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The animal in the photos is actually a female of Osmia cornuta. The horns are quite visible, which makes us exclude Osmia bicolor, and the thorax is entirely covered with black hair, which makes us exclude Osmia bicornis.

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  • $\begingroup$ You are right, I mentioned this options in the comments to the other answer, but wasn't 100% sure. I spent some time observing those bees in the past few days and their behavior completely matches the behavior of Osmia cornuta. Fascinating creatures, never thought bees could be so big and hairy $\endgroup$ – lawful_neutral Mar 29 at 12:19
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Your pictures are quite blurry, but I think this is an Osmia, ie a Mason bee (and not a bumble bee). I think you can see a tendency of the “horns” that female Osmia bicornis (red mason bee) have on their heads on your pictures, so this is my guess. Females are much larger and generally darker than males on the thorax and head, and often quite black there while overall red on the abdomen. Another option is O. bicolour, where females lack the “horns”of bicornis.

See eg this picture: enter image description here

Head picture of female O. bicornis, to see the “horns” clearly (if it is indeed this species): enter image description here
(Pictures from artportalen.se)

Another possible species in the same genus is Osmia bicolor (two-coloured mason-bee), which is more clearly divided in black-orange, see e.g.:

enter image description here

This species has an interesting biology, in that it is specialized on using snail shells for egglaying and preparing larval cells stored with food.

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  • $\begingroup$ It looks similar on these two pictures, but completely different on other pictures of Osmia bicornis that I found. I'll take a closer look tomorrow and try to take better pictures to compare them. $\endgroup$ – lawful_neutral Mar 25 at 20:48
  • $\begingroup$ They can differ quite a bit, but I find the pictures on e.g the wiki-page to be relatively unrepresentative. Look for the female “horns” in large, dark individuals, since this is diagnostic. $\endgroup$ – fileunderwater Mar 25 at 20:55
  • $\begingroup$ Pictures here are also ok (with good info): bumblebeeconservation.org/redmasonbee Also note that this is an yearly spring species, common in the first-flowering plants, so it fits your late-March observations. $\endgroup$ – fileunderwater Mar 25 at 21:00
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    $\begingroup$ Check Osmia bicolor as well (which is more clearly black-orange), but similar in overall body (e.g. artportalen.se/MediaLibrary/2019/5/…). The reason I went for O. bicornis was the possible hints of the horns in your picture. However, sharper images would probably clear up the issue. $\endgroup$ – fileunderwater Mar 25 at 21:28
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    $\begingroup$ I updated pictures in the post, looks very similar to Osmia bicolor $\endgroup$ – lawful_neutral Mar 26 at 13:05

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