B. bohemicus belongs to the subgenus Psithyrus, or the cuckoo bees, which includes 29 species found in Europe and the New World.

Psithyrus was historically considered a separate genus from Bombus due to the significant biological and morphological differences associated with its parasitic life cycle.

[8] The defining physical trait in comparison to non-Cuckoo bumblebees is that B. bohemicus lacks corbiculae, or pollen sacks, on its posterior tibia, instead the area is covered in dense hair.

[8] Females have very thick cuticles, longer and more powerful stings, and larger venom sacs and Dufour's glands compared to its host species.

This bumblebee is distributed through most of Europe, from within the Arctic Circle to northern Spain and Greece[11] and from Britain and Ireland in the west to eastern Russia.

[13] This threshold has not been accurately quantified, but areas of low host population density have been observed to be free of cuckoo-bee parasites.

[15] B. bohemicus is a generalist parasite, invading the nests of B. locurum, B. cryptarum, and B. terrestris,[3] and so is attracted to the chemical signals of any of these potential host species.

[15] This generalist approach gives B. bohemicus more options, which has allowed it to occupy such a large geographical area, but it also has a lower success rate than other members of Psithyrus.

[16] When B. bohemicus females were artificially introduced to freely-foraging early-stage colonies of B. lucorum, the introduced female refused to remain with the host nest, despite a lack of host bee response,[8][16] suggesting a specific selection mechanism, rather than random selection or simply the one initially encountered, that is not fully understood.

[8] B. bohemicus and other Psithyrus queens have a more powerful sting and mandibles as well as generally thicker exoskeleton than their hosts, granting an advantage in conflicts.

[13] The invading queen allows the growth of a sufficient number of host workers, typically one or two broods, to perform the necessary tasks of a functional nest.

[16] B. bohemicus maintains the division of labor in the host nest, as it does not produce any workers to perform foraging, brood-rearing, or defensive tasks.

[16] B. bohemicus must stabilize its presence as the dominant reproductive female, so workers continue nursing behaviors and do not begin to lay their own eggs.

[3][18] The second hypothesis is that these chemicals are in fact applied to workers' bodies by the invasive queen as she takes over to establish herself as the reproductively dominant individual.

[3] The small and stingless males lack the physical defensive abilities of females, as well as a Dufour's gland to produce mimicking chemical signals.

[10] Additionally, males are more easily recognizable as a different species due to their species-specific cephalic secretions that serve as their sexual marking pheromones.

[10] In response, B. bohemicus and other Psithyrus bumblebees have incorporated worker-repellant chemicals into their cephalic secretions, which reduce host worker aggression towards male young.

[10] It is hypothesized that during reproduction, males transfer some of these chemicals to females, which in turn aids in future infiltration into host nests the following cycle.

[16] The parasite queen will attempt to defend her brood by pushing host workers away while buzzing aggressively, and with frequent cell examination.

[3] The invasive queen is not necessarily killed after dominance is lost, but may remain in the hive, either incubating host cocoons or sitting inactively beside the comb.

Since bees identify nest members by scent and other chemical signals, rather than visual appearance, this similarity is instead considered to be Müllerian mimicry.

[14] More important to their success as parasites is their ability to chemically camouflage within their host nest to avoid detection and repulsion during their initial entry.

It shows preference to a diverse selection of scrub-type food plants across its large geographical range,[12] such as: thyme, scabious, knapweed, ling, lavender, masterwort, marsh, and thistles for the male, and sallow, dandelion, clover, bilberry, sycamore, cornflowers, bistort, bugle, thyme, cotoneaster, heath, and raspberry for the female.