Bombus terrestris group
background and definition

Last update: 16 October 2023


Before the rise of DNA profiling, morphological characteristics were the primary way to identify most insects. In bumblebees the colour pattern is an important characteristic [Gokcezade et al. 2010]. However there are species with similar colour patterns and subtle differences that make it difficult to separate them. Such species are called cryptic species.

In the Europe region there is such a group that contains important pollinators:

  • Bombus terrestris
  • Bombus lucorum (Lucorum complex)
  • Bombus magnus (Lucorum complex)
  • Bombus cryptarum (Lucorum complex)
  • Bombus sporadicus (not in the Netherlands (Scandinavia), outside scope of this article)

The species marked with ‘Lucorum complex‘ make up the Lucorum complex, a group of species that resemble each other in such a way that it has been long debated in the past whether there were one or more species involved.

With the development of DNA profiling many bumblebees have been re-analysed and this yielded the confirmation that the Lucorum complex does indeed hold separate species [Williams et al. 2012]. However the DNA analyses also showed that previous determination based on morphological traits were wrong and species actually belonged to a different species [Williams et al. 2012]. This fact raised the question how reliable determinations based on morphological traits are for this and other cryptic groups and whether it is at all possible to identify these species bases on them.
This article is a summary of the current state of affairs with regards to the answer on that question.

The use of the term ‘the species’ in this article references to the first four species listed above unless specified differently.

Examples of colour variation with the species of the group

2. Bombus terrestris GROUP

Based on the latest scientific results it is not possible in principle to determine the species in the field or using photographs based on morphological traits since these overlap [Williams et al. 2012],[Carolan et al. 2012],[Bossert 2014].

However there can be exceptions in local variations, which turns out to be applicable to some extend on the Dutch context wherein a few characters exist that can be used to identify queens and males [Alferink et al. 2020].

The site uses the term ‘Aardhommel groep’ for observations that cannot be identified with certainty. Kerfdier uses the terms ‘Bombus terrestris group’ inside the Netherlands and ‘Bombus terrestris group Western-Europe’ outside the Netherlands. 

Forewing vein analysis

Determination using the vein patterns on forewings proves to be able to identify all bumblebee species, including those mention in this article [Kozmus 2011], [Meulemeester 2009].
However the used scan method requires the removal of the forewing which is than statistically analysed using software [Kozmus 2011]. This renders the method inapplicable in the field and on photographs.


This chapter summarizes the usual morphological traits used in species identification per gender, the status after comparison with DNA identification and the application within the Dutch context.



The used traits of the pile are [Carolan et al. 2012]:

  • does or does not extend below the tegula
  • the side does or does not have an S-shape of black hairs
  • does or does not have melanism in the pile hairs

All traits can occur in the species of the Lucorum complex, with the highest chance for B. cryptorum [Carolan et al. 2012], [Bossert 2014]. The overlap of the traits between species is significant and there cannot accurately identify the species [Carolan et al. 2012].

Unverified traits

Rasmont describes a list of differences in form and details of body parts, however all of them have not yet been verified using DNA analyses and are therefore unreliable [Carolan et al. 2012], [Rasmont 1984]. Also most of these characters are not visible in the field or on photographs [Rasmont 1984].

  • Cheek length
  • Labrum shape and details
  • Clypeus punctuation
  • Ocelli diameter and punctuation
  • Metabasitarsus shape
  • Tergite 2 surface structure
  • Wing colouration and opacity
  • Hair length and grouping
  • Waist size

Validity in Dutch context [Alferink et al. 2020]

Is the pile extended below the tegula than the species is B. magnus.
Is an S-shape of black hairs present than the species is B. cryptarum.
If none of these characters are present DNA analysis needs to identify the species.



The traits mentioned for queens also apply to workers [Rasmont 1984]. However the pile colour and S-shape are more unreliable than in queens [Bossert 2014].
The shape of the labrum and punctuation of the 2nd tergites seem promising traits that need to be validated with DNA research.
For B. magnus workers the yellowish hair on the 1st tergite is a trait that needs to be further investigated [Bossert 2014].

Validity in Dutch context [Alferink et al. 2020]

The workers can only be identified using DNA analysis.



The colour of the facial hairs was a primary trait for the identification of males, but turned out unreliable as it overlaps due to large variation between the species of the Lucorum complex species [Bossert 2014],[Rasmont 1984].
Additionally the males of B. terrestris have black facial hairs, a trait that overlaps with a B. cryptarum male variant that has similar coloured facial hairs.

Possible other drone traits that are used but not yet validated by DNA research are [Rasmont 1986]:

  • Punctuation of the 2nd tergite
  • Ocelli diameter
  • Shape of the 7th sternite

Validity in Dutch context [Alferink et al. 2020]

Does the face have a moustache of yellow hairs and are yellow hairs present on the scutellum, than the species is probably B. magnus.
Does the face have many yellow hairs, than the species is probably B. lucorum.
If none of these characters are present DNA analysis needs to identify the species.


[Gokcezade et al. 2010] Gokcezade, J & Gereben-Krenn, B.-A & Neumayer, Johann & Krenn, Harald. (2010). Feldbestimmungsschlüssel für die Hummeln Österreichs, Deutschlands und der Schweiz (Hymenoptera, Apidae). Linzer Biologische Beiträge. 42.

[Williams et al. 2012] Williams, Paul & Brown, Mark & Carolan, James & An, Jiandong & Goulson, Dave & Aytekin, A. & Best, Lincoln & Byvaltsev, Alexandr & Björn, Cederberg & Dawson, Robert & Huang, Jiaxing & Ito, Masao & Monfared, Alireza & Raina, Rifat & Schmid-Hempel, Paul & Sheffield, Cory & Sima, Peter & Xie, Zhenghua. (2012). Unveiling cryptic species of the bumblebee subgenus Bombus s. str. worldwide with COI barcodes (Hymenoptera: Apidae). Systematics and Biodiversity. 10. 21-56. 10.1080/14772000.2012.664574.

[Carolan et al. 2012] Carolan, James & Murray, Tomás & Fitzpatrick, Úna & Crossley, John & Schmidt, Hans & Björn, Cederberg & Mcnally, Luke & Paxton, Robert & Williams, Paul & Brown, Mark. (2012). Colour Patterns Do Not Diagnose Species: Quantitative Evaluation of a DNA Barcoded Cryptic Bumblebee Complex. PloS one. 7. e29251. 10.1371/journal.pone.0029251.

[Bossert 2014] Bossert, S. (2014). Recognition and identification of species in the Bombus lucorum-complex – A review and outlook.

[Rasmont 1984] Rasmont, Pierre. (1984). Les Bourdons du genre Bombus Latreille sensu stricto en Europe Occidentale et Centrale (Hymenoptera, Apidae). Spixiana. 7. 135-160.

[Rasmont 1986] Rasmont, Pierre & A., Scholl & De, Jonghe & E., Obrecht & A., Adamski. (1986). Identité et variabilité des mâles de bourdons du genre Bombus Latreille sensu stricto en Europe occidentale et centrale (Hymenoptera, Apidae, Bombinae). Revue suisse de zoologie; annales de la Société zoologique suisse et du Muséum d'histoire naturelle de Genève. 93. 661-682. 10.5962/bhl.part.79505.

[Kozmus 2011] Kozmus, Peter & Virant-Doberlet, Meta & Meglic, Vladimir & Dovc, Peter. (2011). Identification of Bombus species based on wing venation structure. Apidologie. 42. 472-480. 10.1007/s13592-011-0037-5.

[Meulemeester 2009] De Meulemeester, Thibaut & Aytekin, A. & Valterová, Irena & Rasmont, Pierre. (2009). Landmark based geometric morphometrics analysis of wing shape as a tool for Bombus s.str. taxonomy (Hymenoptera:Apidae).

[Alferink et al. 2020] Lucas Alferink, Leon Marshall, Roland De Jonghe, et al. Distinguishing white-tailed bumblebees in the Netherlands: morphology, ecology and DNA-barcoding. Authorea. September 10, 2020.

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