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As far as I understand, this is a buff-tailed bumble bee (Bombus terrestris). It was collected (dying) inside my house in Santiago, Chile. The species was intentionally introduced not far away, for agriculture, some years ago.

Looking for descriptions, I see it is huge for its species, queens reportedly being 20-22 mm (1, 2). I also learned that workers span a wide range of sizes, depending on age (but not this large, supposedly.)

Now, for the caste/sex, I'm stuck due to lack of experience. This site suggests looking at pollen baskets in the hind legs for females (I think I see one, but can't be sure since I don't know exactly what to look at, despite browsing some example photos), but then hairy hind legs (again, I think I might see them, but I'm much less confident) and facial hair for males (I don't really have a point of comparison, but it has some short, black hair in the frons: see expanded photo). Common descriptions also suggests buff color for the tails for queens, but I have seen white-tailed queens around too.

I'd really like to acquire the experience needed.

Is this an old worker, or something else?

maybe 23 mm long?

enter image description here

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    $\begingroup$ this is very likely a queen as they are 20-23mm long but to give a definitive answer you need to measure the lenght of the wings,if they are 38-43 mm it is a queen.the body of a male is 14-16mm the lenght of the wings are 30-33mm and the workers are 11-17mm long and the wings are 22-34 mm long.this is not an answer only some easy to find information. $\endgroup$ Jun 3 at 16:56
  • $\begingroup$ @trondhansen, thank you! I also read that queens are supposed to have a shorter tongue, which doesn't seem to be the case. I was wondering if there could have been a selective pressure towards larger individuals, vaguely analogous to leg length in cane toads in Australia $\endgroup$
    – Rafael
    Jun 3 at 17:39
  • $\begingroup$ I mean, introduction is still relatively recent. Wingspan is about 45 mm BTW (about twice the body length, like all three queens, workers and males) $\endgroup$
    – Rafael
    Jun 3 at 17:46

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