Bombus

B. terricola queen resting.

Bombus in the strict sense ecology and behaviour   HABITAT: Forest-edge, mountain meadow, and grassland.   FOOD-PLANTS: Short tongue-length bumblebees visiting shallow flowers. They frequently bite holes in corollas and rob deeper flowers. They also provide 'buzz' pollination. B. terrestris is widely propagated and introduced for the pollination of glasshouse crops.   NESTING BEHAVIOUR: Nests underground. Non-pocket makers. Colonies may be large.   MATE-SEARCHING BEHAVIOUR: Males patrol circuits of scent marks.

Subgenus BOMBUS in the strict sense
[Bremus [Jurine], 1801:164, type-species Apis terrestris Linnaeus = Bombus terrestris (Linnaeus) by subsequent designation of Morice & Durrant, 1915:429, suppressed by ICZN, 1939]
[Bremus Panzer, [1801-1804]:pl.19-21, type-species Apis agrorum Fabricius = Bombus pascuorum (Scopoli) by subsequent designation of Sandhouse, 1943:532, suppressed by ICZN, 1954]
Bombus Latreille, 1802:437, type-species Apis terrestris Linnaeus [cited as Apis terrestris F.] = Bombus terrestris (Linnaeus) by monotypy
Bombus Latreille, 1802:385, type-species Apis terrestris Linnaeus = Bombus terrestris (Linnaeus) by monotypy, redescribed
Bombus (Leucobombus) Dalla Torre, 1880:40, type-species Apis terrestris Linnaeus (= Bombus terrestris (Linnaeus)) by subsequent designation of Sandhouse, 1943:564
Bombus (Terrestribombus) Vogt, 1911:55, type-species Apis terrestris Linnaeus (= Bombus terrestris (Linnaeus)) by subsequent designation of Frison, 1927:67
[Bombellus Zoological Record, 1931:248 ?published without description]

Part of the bumblebee phylogenetic tree including available Bombus s. str. species from an analysis of DNA sequence data for five genes (Cameron et al. 2007 [pdf]). Values above branches are Bayesian posterior probabilities, values below branches are parsimony bootstrap values. Alternative resolution from parsimony analysis is shown with dotted lines.

Bombus (Bo.) sporadicus Nylander
sporadicus Nylander, 1848:233
malaisei Bischoff, 1930:4
23 names

MORPHOLOGY: photos of male genitalia.

DISTRIBUTION: Oriental, Palaearctic Regions.

Bombus (Bo.) ignitus Smith
ignitus Smith, 1869:207, examined
terminalis Smith, 1873:206, examined, not of Smith in Horne, 1870:193 (= B. festivus Smith)
japonicus Dalla Torre, 1890:139, replacement name for terminalis Smith, 1873:206
15 names

MORPHOLOGY: photos of male genitalia.

DISTRIBUTION: Oriental, Japanese, Palaearctic Regions.

Bombus (Bo.) tunicatus Smith
tunicatus Smith, 1852a:43, examined
vallestris Smith, 1878:8
gilgitensis Cockerell, 1905:223, examined
?manaliensis Kumar & Lall, 2004:236
12 names

MORPHOLOGY: photos of male genitalia.

DISTRIBUTION: Oriental Region.

Bombus (Bo.) terrestris (Linnaeus)
terreftris [terrestris] (Linnaeus, 1758:578 [Apis])
Audax (Harris, 1776:130 [Apis]) not of Harris, 1776:137 (= Anthophora sp.)
canariensis Pérez, 1895:191
maderensis Erlandsson, 1979:191
109 names

TAXONOMIC STATUS: B. terrestris, B. maderensis and B. canariensis have been regarded both as conspecific and as separate species.

Erlandsson (1979) argued that the dark individuals from the Canary Islands, previously placed within B. terrestris by for example Krüger (1954, 1956), are a separate species, B. canariensis. Erlandsson also argued that individuals from the island of Madeira, previously placed within B. terrestris by Bischoff (1937), are a separate species, B. maderensis. In both cases the morphological characters used to support these distinctions are not strongly divergent from the broad variation within B. terrestris in the broad sense. Rasmont (1984) also regards these three taxa as separate species, but Pekkarinen & Kaarnama (1994) treat them as conspecific.

Recent work by Estoup et al. (1996) has found that although mainland populations do not vary significantly among themselves in mitochondrial genes, all island populations studied (from six Mediterranean islands with near-typical B. terrestris in addition to B. canariensis) show significant differences from the mainland populations.

Consequently, viewing these three nominal taxa as separate species may be one interpretation, but this appears to depend on adopting a very narrow species concept that admits little colour, morphological, or genetic variation within a species, and regards current geographical isolation as highly indicative. I prefer to regard these taxa as conspecific until further evidence is available.

NOMENCLATURE: The orthography of Linnaeus (1758) employs a long 's' (similar to 'f' or 'f'), a common practice of the period. This convention has since changed and recent authors have consistently used 's'.

Day (1979) described how none of the admissable syntypes of A. terrestris Linnaeus is in agreement with the current usage of the name.

To reaffirm the traditional usage of this particularly widely used name, a case was made to ICZN by Løken et al. (1994). This sought an Opinion from ICZN (ICZN, 1996) that set aside, by use of its Plenary Power (ICZN, 1985: Articles 78b, 79), the lectotype designation for A. terrestris by Day from application of the Code (ICZN, 1985), and then designated a neotype (ICZN, 1996: 64) to conserve the traditional usage of the name for even the narrowest concept of the taxon (ICZN, 1985: Article 75).

MORPHOLOGY: photos of male genitalia.

DISTRIBUTION: Palaearctic Region.

INTRODUCTIONS: This species has been introduced into New Zealand (e.g. Gurr, 1957, 1995; Macfarlane & Gurr, 1995) (see the comments on B. hortorum, B. ruderatus, and B. subterraneus), Tasmania (Cardale, 1993; Stout & Goulson, 2000), Brazil (Thorp, 2003), Chile (Torretta et al., 2006), Mexico (Stout & Goulson, 2000; Winter et al., 2006), and Japan (Washitani, 1998; Inoue et al., 2008). It appears that it was also introduced into mainland Australia (New South Wales) without persisting (W. Froggatt in Franklin, 1913). Recently it has spread from Chile to Argentina (Torretta et al., 2006).

NOTES on this species in Britain.

Bombus (Bo.) hypocrita Pérez
hypocrita Pérez, 1905:30
16 names

MORPHOLOGY: photos of male genitalia.

DISTRIBUTION: Oriental, Japanese, Palaearctic Regions. This species has shown dramatic declines in its former range and abundance in Japan since the introduction there of B. terrestris (Matsumura et al., 2004; Inoue et al., 2008).

Bombus (Bo.) affinis Cresson
affinis Cresson, 1863:103
3 names

MORPHOLOGY: photos of male genitalia.

DISTRIBUTION: E Nearctic Region. This species has shown a precipitous collapse in its former range and abundance since 1995 (Thorp, 2003; Thorp & Shepherd, 2005; Colla & Packer, 2008).

IUCN CONSERVATION STATUS: Preliminary assessment as CRITICALLY ENDANGERED (Williams & Osborne, 2009) by criterion A2 (IUCN, 2001, 2008) that it is inferred to have undergone a >80% population reduction since 1995, that the causes may not be reversible and may not yet have ceased, based on few records of individuals in the last four years. The last record known to me is from 2008 (J. Ascher; S. Cameron; S. Colla, in litt.).

Bombus (Bo.) franklini (Frison)
franklini (Frison, 1921:147 [Bremus]) examined
1 name

TAXONOMIC STATUS: This species has been treated as conspecific with B. occidentalis (= B. terricola) by Milliron (1971), but has since been shown to be very distinct in morphology by Plowright & Stephen (1980) and Williams (1991 [pdf]), and in enzyme mobilities by Scholl, Thorp & Obrecht (1992).

MORPHOLOGY: photos of male genitalia.

DISTRIBUTION: W Nearctic Region. B. franklini has one of the narrowest distributions of any bumble bee species world-wide. All recent specimens have been collected within a 60 mile (97 km) radius of Grants Pass, Oregon (Thorp, 1970, 2003, 2005; Thorp et al., 1983). This species has shown dramatic declines in its former range and abundance since 1995 (Thorp, 2003, 2005; Thorp & Shepherd, 2005; IUCN, 2008).

IUCN CONSERVATION STATUS: Preliminary assessment as CRITICALLY ENDANGERED (Williams & Osborne, 2009) by criterion A2 (IUCN, 2001, 2008) that it is inferred to have undergone a >80% population reduction since 1995, that the causes may not be reversible and may not yet have ceased, based on few records of individuals in the last four years. There are suggestions that it may be extinct (Buchmann et al., 2008). The last record known to me is from 2006 (R. Thorp, in litt.).

Bombus (Bo.) terricola Kirby
Terricola Kirby, 1837:273
?occidentalis Greene, 1858:12
9 names

TAXONOMIC STATUS: B. terricola and B. occidentalis have been regarded both as conspecific (e.g. Milliron, 1971; Poole, 1996) and as separate species (e.g. Franklin, 1913 [but see p. 239]; Stephen, 1957; Thorp et al., 1983; Scholl et al., 1990) (click here for colour variation diagrams for workers).

In the first major taxonomic review, Franklin (1913:239) wrote of B. terricola and B. occidentalis (among other taxon pairs): "the relationships are evidently very close, the differences, while apparently constant, being so small that it must be entirely a matter of personal opinion whether they should be given full species rank or be considered as only subspecies...[p. 240] If some other worker should reduce [the species to subspecies], the writer could present no very substantial reasons why they should not be so classified." Since then, Franklin's understandable but essentially arbitrary decision has tended to become increasingly set in stone as it was repeated, despite little in the way of systematic and continent-wide studies to bring further documented evidence to the discussion. One reason may be that most people's experience of these bees comes from the far east and the far west of the range, while few people examine specimens from across the entire range.

Increasing availability of specimens from across North America makes justifying recognising B. terricola and B. occidentalis as two separate species on the grounds of a slight difference in colour pattern alone increasingly difficult. Franklin (1913:276) distinguished the two by a completely yellow tergum II in B. terricola compared to some black on tergum II in B. occidentalis. However, available specimens appear to show a cline in colour variation between the eastern B. terricola colour pattern and the western B. occidentalis colour pattern. Many specimens from the north west of North America show a reduction in the extent of the yellow bands on gastral terga II and III, with an expansion of the pale pubescence on tergum IV, which appear to be intermediate or recombinant individuals between the two extreme patterns (patterns 3-5 from the left of the pattern diagrams here). Indeed, Stephen's (1957:74) figure 4 shows several patterns that could represent a continuum of variation between the two forms. Furthermore, Thorp et al. (1983: fig. 140a) illustrate individuals of 'B. occidentalis' from California that look very similar to eastern B. terricola. In view of this, Stephen's conclusion that there is no intergradation may result from adopting colour criteria (identifying B. terricola in the strict sense either by completely black pubescence of female terga V-VI [p. 15] and male tergum IV [p. 19], or by completely yellow pubescence of tergum II [pp. 19, 71], two character states that do not always occur together, even in the east) that could be considered as essentially arbitrary points on a continuum (see also the comments on B. fervidus).

Evidence from comparisons of DNA sequences from the 16S gene is consistent with the two taxa being conspecific (Cameron et al., 2007 [pdf]). However, simple genetic-distance thresholds do not relate directly to accepted species concepts and therefore are not generally accepted as a valid criterion for recognizing species.

Ultimately the problem is that none of the published studies on B. terricola and B. occidentalis to date actually address the issue directly by deriving appropriate criteria from species concepts and then testing the bees in a rigorous and quantitative manner against these criteria. In view of the existence of apparent intermediates between these nominal taxa in at least part of their range in the characters used to recognise them, they are treated here as likely to be conspecific. Until more evidence to the contrary is available from critical studies of patterns of variation from across the range, I shall treat them as parts of a single variable species.

MORPHOLOGY: photos of male genitalia.

DISTRIBUTION: W Nearctic, E Nearctic Regions. This species has shown dramatic declines in range and abundance particularly in the south west and south east of its former range since 1995 (Thorp, 2003; Thorp & Shepherd, 2005; Colla & Packer, 2008).

IUCN CONSERVATION STATUS: Preliminary assessment as ENDANGERED (Williams & Osborne, 2009) by criterion A2 (IUCN, 2001, 2008) that it is inferred to have undergone a >50% population reduction since 1995, that the causes may not be reversible and may not yet have ceased, based on few records of individuals in the last four years, at least in the south-eastern and south-western quarters of its range.

Bombus (Bo.) patagiatus Nylander
patagiatus Nylander, 1848:234
lan-tschóuensis [lantschouensis] Vogt, 1908:101
vasilievi Skorikov, 1913:172
28 names

MORPHOLOGY: photos of male genitalia.

DISTRIBUTION: Oriental, Japanese, Palaearctic Regions.

Bombus (Bo.) lucorum (Linnaeus) complex
lucorum (Linnaeus, 1761:425 [Apis]), examined
?cryptarum (Fabricius, 1775:379 [Apis])
?modestus Cresson, 1863:99, not of Eversmann, 1852:134 (= B. modestus Eversmann)
?moderatus Cresson, 1863:109, replacement name for modestus Cresson, 1863:99
monozonus Friese, 1909:674
?magnus Vogt, 1911:56
?jacobsoni Skorikov, 1912:610, examined
?burjaeticus Krüger, 1954:277
?florilegus Panfilov, 1956:1334
?reinigi Tkalcu, 1974b:322, examined
186 names

TAXONOMIC STATUS: These bees have received particularly close attention by authors describing the minutiae of colour variation, using at least 186 classical names (see the introduction).

In Europe, at least some of these nominal taxa are regarded as separate species by some authors (e.g. Rasmont, 1983, 1984, 1988; Scholl & Obrecht, 1983; Scholl et al., 1990; Scholl, Thorp & Obrecht, 1992; Rasmont et al., 1995; Amiet, 1996; Özbek, 1997; Pamilo et al., 1997; although B. cryptarum and the North American B. moderatus have recently been treated as conspecific with B. lucorum by Poole, 1996). Nonetheless, there are conflicting patterns of variation among some characters of these taxa, which are not fully understood (Pekkarinen, 1979; Pamilo et al., 1984; Amiet, 1996; Baker, 1996a; Pamilo et al., 1997) and in Britain queens of these taxa appear to show almost a continuum of colour variation (Williams, 2000). Recent studies of DNA (the COI gene) sequences (e.g. Murray et al., 2008) are consistent with B. lucorum, B. magnus and B. cryptarum being three separate species in Europe, although there are still no reliable colour or morphological characters for diagnosing workers and males.

In Central, Southern, and Eastern Asia, there appears to be an even greater problem. In some regions there is a broad range of morphological variation, with what appears to be intergradation of character combinations (Williams, 1991:86 [pdf]). Evidence from DNA sequences from five genes from a very few samples is consistent with more than one taxon being likely to be involved there too (Cameron et al., 2007 [pdf]).

From the evidence available at present, the separation of taxa, the recognition of species, and the nomenclature of those species, are still all unreliable, so there remains an urgent need for this species complex to be revised throughout its range world-wide. Thus, as a conservative temporary measure, the name B. lucorum is applied here in its broadest sense, to include the entire complex of similar nominal taxa.

NOMENCLATURE: When Day (1979) came to fix the application of A. terrestris Linnaeus (see the comments on B. terrestris), he had no reason to believe that Linnaeus had not described this taxon from the syntype specimen that was subsequently described as the lectotype (= A. cryptarum Fabricius, see Rasmont, 1988:52, ?= B. lucorum (Linnaeus)). This action brought B. lucorum (Linnaeus) into subjective junior synonymy with B. terrestris (Linnaeus).

To reaffirm the traditional usage of B. terrestris and B. lucorum, a case was made to ICZN by Løken et al. (1994). This sought an Opinion from ICZN (ICZN, 1996) that set aside, by use of its Plenary Power (ICZN, 1985: Articles 78b, 79), the lectotype designation for A. terrestris by Day from application of the Code (ICZN, 1985), and then designated a neotype (ICZN, 1996: 64) to conserve the traditional usage of B. terrestris and B. lucorum (ICZN, 1985: Article 75).

MORPHOLOGY: photos of male genitalia.

DISTRIBUTION: Oriental, Japanese, Palaearctic, Arctic, W Nearctic Regions.

INTRODUCTIONS: This species occurs in Iceland, where it has probably been introduced (Prys-Jones et al., 1981) (see the comments on B. hortorum).

NOTES on this species in Britain.