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Article

Spread and Ecology of the Bumblebee Bombus haematurus (Hymenoptera: Apidae) in Northeastern Italy

by
Elena Cargnus
1,*,
Marino Quaranta
2,
Alberto Villani
3 and
Pietro Zandigiacomo
1
1
Department of Agricultural, Food, Environmental and Animal Sciences (DI4A), University of Udine, Via delle Scienze 206, 31000 Udine, Italy
2
CREA—Council for Agricultural Research and Economics, Research Centre for Agriculture and Environment, Via di Corticella 133, 40128 Bologna, Italy
3
Agenzia Regionale per la Protezione dell’Ambiente—s.o.c. OSMER e GRN, Via Natisone 43, 33057 Palmanova, Italy
*
Author to whom correspondence should be addressed.
Diversity 2025, 17(8), 534; https://doi.org/10.3390/d17080534
Submission received: 24 June 2025 / Revised: 25 July 2025 / Accepted: 26 July 2025 / Published: 30 July 2025
(This article belongs to the Special Issue Diversity in 2025)
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Versions Notes

Abstract

Bombus haematurus (Hymenoptera: Apidae), which arrived from the Balkan Peninsula, was first reported in Italy in 2020 in the Friuli Venezia Giulia region (FVG) (northeastern Italy) near the border with Slovenia. To study the spread and biology of the species, a survey was conducted at several sites of the FVG in the period 2023–2025. Bombus haematurus was recorded at 22 new sites across all four districts of the FVG (Trieste, Gorizia, Udine, and Pordenone), indicating its expansion towards the west. Bumblebees of this species were detected in plain and hilly areas at sites between 10 and 364 m a.s.l. They were observed more frequently at forest edges, undergrowth paths or clearings and meadows adjacent to woods, confirming the species is hylophilous. The activity of adults from February to July confirms that the bumblebee is an univoltine spring species. Specimens were observed foraging on the flowers of 19 wild and ornamental plants belonging to 12 families (in particular, Lamiaceae), confirming that the species is polylectic. The data collected indicate that B. haematurus are permanently established in the FVG and that a further spread of the species towards the west in the neighbouring Veneto region is likely.

1. Introduction

The blood-tailed bumblebee, Bombus (Pyrobombus) haematurus Kriechbaumer, 1870 (Hymenoptera: Apidae), unlike most other bumblebee species, in recent decades has expanded its distribution by approximately 1000 km from its native range, namely southeastern Europe, Turkey, and Iran, towards central and western Europe, reaching Slovakia, the Czech Republic, Austria, Slovenia, and Italy [1,2,3,4,5,6] (Figure 1). Most recently, B. haematurus has also been observed in Poland [7]. This rapid geographic dispersal of the bumblebee appears to benefit from global warming as mild winters and favourable ecological conditions in spring allow its expansion toward northern Europe [4,8,9].
In Italy, before the present study, the only known records for B. haematurus were limited to a few sites in the eastern part of the Friuli Venezia Giulia region (FVG) bordering Slovenia, three sites in 2017 [6] and one site in 2021 [10].
This generalist pollinator, previously described as a steno-hylophilous species [11], nowadays appears to be more of an euryoecious-hylophilous species, having been observed in a variety of habitats beyond forests, including orchards, grasslands, and park-like environments [3,4,8,12,13]. Nests are built in trees or under the ground’s surface, in abandoned rodent holes or artificial nest boxes [13,14,15].
According to current taxonomic knowledge, 79 species of bumblebees are known from the West Palaearctic region, with 68 species reported in Europe [4,16,17,18]. In Europe, bumblebees represent approximately 3.2% of the total Apoidea fauna (i.e., 2138 species [19]). In Italy, 44 bumblebee species, 4.2% of the national Apoidea fauna, have been reported [18,19,20,21], with 32 species recorded specifically in the FVG region [22]. However, both national and FVG species lists require updates due to taxonomic revisions and recent faunistic findings [23].
Following the first records of B. haematurus on the eastern border of the FVG reported in the literature [6], a study was initiated to monitor its colonisation pattern across the region and to collect ecological data, including habitat preferences, flight period, and visited flowering plants.

2. Materials and Methods

After a new single discovery of a specimen in June 2022, we decided to survey the distribution of B. haematurus in the FVG from February 2023 to March 2025 at 37 sites across the four regional districts: Trieste, Gorizia, Udine, and Pordenone. Data were collected up to March 2025 to cover the emergence of overwintering queens over three different years. The study sites were distributed across an area of approximately 3500 km2 within the regional territory and located at varying altitudes, from plains to hills, diverse habitats within natural and semi-natural landscapes featuring seasonal flowering vegetation. To check the presence of B. haematurus, the sites were visited once or more times according to the following scheme. The sites where the species was detected during the initial visit were typically not resampled. In contrast, sites where the bumblebee was not observed initially were revisited, and the surrounding areas were checked as well. If the bumblebee was still not detected, this confirmed the previous observation of its absence at that location. The list of study sites, the number of visits per site in the same or different years, and environmental features are reported in detail in Table 1, Tables S1 and S2. Additional inspections at several sites where B. haematurus was present were useful in collecting preliminary data on the species’ flight period within our region (Table 1). In 2024 and 2025, two sites (GO2 and UD1; Table 1 and Table S1) were monitored weekly from mid-February until the emergence of the first overwintering queens.
The time spent searching for B. haematurus at each site, under favourable weather conditions (sunny and calm or moderately windy days), varied depending on the location. Typically, at each sampling date, if no individuals were detected after walking for 1 km for at least one hour and surveying an area of 3000–5000 m2, the species was considered absent from that site. Depending on the season, sampling was preferably carried out either in the morning or in the mid to late afternoon (between 9:00–11:00 or 15:00–18:30, local time).
Specimens were identified as B. haematurus following Pittioni [24] and Gokcezade et al. [25]. The diagnostic characters based on body colouration alone [7,25] were observable in the field, allowing for species identification without the need to collect all encountered bumblebees. Consequently, only a representative sample of bumblebees per site was captured as a voucher. The specimens are deposited in the Apoidea collections of Agricultural, Food, Environmental and Animal Sciences (DI4A), University of Udine, and the Research Centre for Agriculture and Environment (CREA), Bologna.
Plants visited by B. haematurus were identified to species level and characterised for the flowering period, and nectar and pollen production using available data in the literature [26,27,28,29,30].

3. Results

3.1. Specimens Recorded and Species Distribution

During the study years (2023–2025), the Bombus haematurus bumblebees (N. 238 adults, of which 112 captured) were found at 22 out of 37 sites visited across the four regional districts of the FVG in northeastern Italy (Table 1, Tables S1 and S2; Figure 2). In the eastern part of the FVG, B. haematurus was recorded in the Isonzo plain of the Gorizia district (sites GO1–6) as well as in the coastal area and the Karst plateau of the Trieste district (sites TS1 and TS2–4, respectively). In the central part of the FVG, the species was found at 10 sites within the Udine district, including the Morainic hills (sites UD1–5), the Julian Prealps (sites UD6,7), and the central Friulian plains (sites UD8–10). To the west, the bumblebee was found in the foothills of the Carnic Prealps in the Pordenone district (sites PN1,2). The highest number of B. haematurus specimens was recorded at site UD1 (N. 147, 62% of the total) as this site was the most frequently visited (16 times) during the present survey (Table 1).
Bombus haematurus was not observed in eight lowland sites and seven hilly sites in the FVG (4–115 and 315–881 m a.s.l., respectively) (Figure 2 and Table S2). These sites included one coastal area (Trieste district), two inner Karst sites (Gorizia district), three central Friulian plains sites (Udine district), three Julian Prealps sites (Udine district), as well as two western Friulian plains sites and four Carnic Prealps sites (Pordenone district).

3.2. Habitats

Bombus haematurus was observed in different habitats (Table 1 and Table S1). The bumblebee was mainly detected in natural areas, such as the edges of deciduous forests, undergrowth paths or clearings and meadows adjacent to woods (15 out of 22 sites) (Table 1 and Table S1). In semi-natural areas (i.e., suburbs and rural landscapes), bumblebees were found within gardens featuring fruit trees or ornamental shrubs (GO1, TS1, and UD3,10), uncultivated margins (UD9) and hedgerows near vineyards (GO5, UD8). However, habitats associated with suburbs and rural landscapes were near woodlands.

3.3. Preliminary Data on the Flying Season

Queens of B. haematurus were observed from mid-February to the end of May, workers from mid-April to early July, and males from mid-May to mid-June (Table 1 and Table S1; Figure 3). The first queen was found in mid-February only at the site TS1 (Trieste suburb), whereas in other sites weekly sampled from February to March (sites UD1 and GO2), the first queens were observed in the first week of March.

3.4. Flowering Plants Visited

Overall, 90% of the B. haematurus specimens were observed foraging on the flowers of 19 species (17 wild and two cultivated as ornamental species) from 12 families, while one worker was active on honeydew produced by aphids infesting the leaves of Malus domestica, and the other 10 specimens were flying above ground level (Table 2 and Table S1). Lamiaceae were widely represented during the samplings at nearly all sites where the bumblebee was present, except in two cases (sites UD6,8). In March, queens initially foraged on the early spring-flowering Lamium purpureum (five sites). From April to June, queens, workers and males were observed visiting L. orvala, L. maculatum, and L. galeobdolon in several sites (see Table S1, Figure 4). During the May to July period, workers frequented Salvia pratensis, S. verticillata, and the ornamental Lavandula angustifolia. In one case, a queen was seen feeding on the ornamental Teucrium fruticans. Both workers and queens observed on Lamium spp. carried yellow- and orange-coloured pollen in corbiculae on their hind legs. In addition to Lamiaceae, queens of B. haematurus foraged on several early-spring-flowering species, such as Asperula taurina, Corydalis cava, Crocus heuffelianus, Erythronium dens-canis, Helleborus odorus, Lathraea squamaria, Scilla bifolia, and Veronica persica (Figure 4). Most of these plants were recorded in the flowering undergrowth of site UD1, as it was the most frequently visited site early in the season (see Table S1). In May and June, a few workers were observed feeding on Echium vulgare, Vicia cracca, and Knautia drymeia, with a male also collected from the latter.
Bombus terrestris (L.), B. pascuorum (Scopoli), and B. argillaceus (Scopoli) were the most frequently recorded bumblebees foraging on the flowering plants alongside B. haematurus at the sites visited.

4. Discussion

The occurrence of B. haematurus at several sites of the FVG (northeastern Italy) suggests a successful and ongoing spread of the species throughout the investigated area. These findings confirm the range expansion of the blood-tailed bumblebee from its native distribution through the Balkans into northwestern Europe. The newly detected populations likely arrived from neighbouring Slovenia, where the species was first recorded over 15 years ago (in 2007) [3] and subsequently inhabited the bordering Gorizia district in Italy (in 2017) [6]. The study confirms the establishment of B. haematurus populations in the eastern part of the FVG (Gorizia district), with queens, workers, and males recorded over four consecutive years (2022–2025) at the visited sites (GO1–5). These findings are further supported by recent observations from the eastern part of the Region (Gorizia and Trieste districts) [10], which agree with the results of the present study. The detection of B. haematurus in the central and western parts of the region (Udine and Pordenone districts) indicates continued westward expansion of the species, which has now reached its westernmost point at 12°49′ E longitude (Pordenone district, site PN2). However, its absence in at least six sites further west suggests that B. haematurus has not yet reached the neighbouring Veneto region. As in our region, the spread of B. haematurus occurs in other central and northern European countries [7,13,31,32].
Bombus haematurus was recorded at altitudes ranging from 10 up to 287 m a.s.l. and, except for a single record in a foothill valley site at 364 m a.s.l. (UD6) of the Julian Prealps, no specimens have been recorded at five higher elevation sites ranging from 408 to 881 m a.s.l. (in the Julian and Carnic Prealps; see data in Table S2). Several occasional checks conducted at the three sites above 800 m a.s.l. suggest that the species is currently absent from these higher altitudes. However, further observation will be necessary to confirm these results. Also in other European countries, Slovenia, Austria, and Slovakia, the species is most commonly found at low altitudes (up to 300–350 m a.s.l.) [1,3,12,13,14], whereas in the native area it occurs at higher altitudes, as reported for southern Balkan Peninsula (900–2000 m a.s.l.) [11], Greece (up to 700 m a.s.l.) [33], Turkey (600–2600 m a.s.l.) [34] or northern Iran (up to 1200 m a.s.l. and accidentally even to 2150 m a.s.l.) [35]. Indeed, it is well known that, according to the principle of latitudinal–altitudinal compensation, bumblebee species that occur at low elevations in northern latitudes are typically found at increasingly higher altitudes toward the south [4,36]. This pattern reflects the species’ thermal preferences and their adaptation to similar climatic conditions across geographic gradients. However, single observations of the bumblebee at higher altitudes (up to 755 m a.s.l.) were recorded in Hungary and Poland [7,13].
This study confirms that the occurrence of B. haematurus in a specific habitat is associated with the presence of deciduous forests and forest edge, which agrees with other studies [3,4,8,12,13]. Specifically, in this study, B. haematurus was frequently observed in natural environments, on herbaceous flowering plants in woodland undergrowth, hedgerows, or meadows on forest edges. In rural and suburban areas, visiting wild flowering herbaceous species under hedgerows alongside farm roads, uncultivated fields or ornamental flowers in gardens is favoured by the proximity of woods to these sites, indicating that B. haematurus is closely related to forest landscapes. These data suggest that B. haematurus is a hylophilous species (of euryoecius type), which agrees with other studies (see [3,4,8,11,12,13]. On the contrary, sites with the presence of flowers but with few wood trees or far from forested areas appeared unfavourable to B. haematurus. For example, this situation occurs at two sites from the Friulian plains in suburban and rural landscapes (Rizzi and Sant’Osvaldo, respectively, Udine district; see data in Table S2) where the bumblebee was absent.
This study presents the first data on the phenology of B. haematurus in Italy. In both the lowland and foothill sites visited in the FVG, the overwintered queens emerged at the end of winter, remaining active until the end of May, with no marked differences in flying duration based on site altitudes (plains vs hills). In particular, in 2024 and 2025, the first queens emerged from their hibernation sites within the first week of March, both in a foothill and a plain site. Regarding these events, similar daily temperatures were recorded for these sites (mean 7.1–11.8 °C, max 12.5–17.0 °C, and min 1.5–6.3 °C) [ARPA-OSMER http://www.osmer.fvg.it/ (accessed on 15 February 2025) at the nearest weather stations to the sites UD1, UD6, GO2]. Queens, males (active from mid-May to mid-June), and workers (active from mid-April to early July) were no longer observed during some samplings conducted in mid-July and August, which could indicate that diapause for this species begins in mid-summer. Therefore, B. haematurus appears to be a univoltine spring species for the study area. Similar data on phenological traits for the species have been detected in Slovenia [15] and Slovakia [13].
The several plants visited by the B. haematurus (19 species of 12 families) allow us to confirm that the species is polylectic, in agreement with observations from other studies [3,8,13,35,37]. As reported in these studies and observed during this survey, the bumblebee visited both deep-corolla flowers with hidden nectar (e.g., several species of Lamiaceae) and flowers with open corollas and more accessible nectar (e.g., E. vulgare and V. persica). However, at a site with flowering E. vulgare and L. angustifolia, B. haematurus foraged exclusively on the former species, while in a meadow scattered with flowering L. purpureum and V. persica, B. haematurus visited both plants. Following the literature, B. haematurus frequently foraged on the flowering Lamium species, such as L. galeobdolon, L. purpureum, and L. maculatum [5,12,13]. The spring flowers of Lamium spp. were the most visited, including L. orvala, which is not reported as a food plant for B. haematurus in the literature. The other flowering species visited by the bumblebee in this study, including ornamental plants, are reported as food plants, at least at the genus level, in other studies (notably C. cava, E. vulgare, L. squamaria, Lavandula sp., S. officinalis, Teucrium sp., V. cracca) [8,14,37,38]. Although A. taurina and L. squamaria are rarely visited by Bombus spp. according to Ricciardelli d’Albore and Intoppa [27], in this study, B. haematurus was observed on both flowering plants and, in the latter, also in other studies [8,39]. The late-winter flowering C. heuffelianus, E. dens-canis, H. odorus, and S. bifolia attracted the overwintering queens, highlighting the significant role of these plants as a food source for the bumblebee before the onset of early-spring flowering Lamiaceae in this geographic area.
The bumblebee visits flowers of woody plants as well (e.g., Prunus spp., Tilia spp., and Viburnum sp.) [3,8,33,35]. Nevertheless, no B. haematurus were recorded foraging on flowers of tree species in this study. The event of a worker consuming aphid honeydew on leaves of an apple tree is like that reported in the study of Šima et al. [13]. Some queens were recorded flying close to the ground; they were likely searching for cavities suitable for nesting.
Bombus haematurus was observed in this study with native Bombus species, mainly B. terrestris, B. pascuorum, and B. argillaceus, on the same flowering plants as already reported in the literature [1,37]. In the study area, competition between B. haematurus and these generalist species for floral resources and nesting sites appears unlikely. This may be partly due to the fact that B. haematurus is an early-season species with a relatively short flight period, as observed in the present study and Biella et al. [8], in contrast to species with long flight periods, such as B. argillaceus (February to October), B. pascuorum (April to September), and B. terrestris (March to October) [22]. However, if B. haematurus spreads into higher-altitude areas in the future, potential competition with more specialized native wild bees could occur.
The expansion of the hylophilous B. haematurus in our region appears to be directed not only westward but also northward; however, the high elevations of the Carnic and Julian Alps, which extend in a west–east direction, constitute a barrier to further northward spread of the species. This pattern of spread may be due to the continuous presence of natural areas characterized by deciduous forest landscapes in the foothills, as opposed to the fragmented woodland areas found in the semi-urban and rural landscapes of the plains to the south of the FVG. In our region, as in other European countries, the expansion of woodland into agricultural land, particularly in hilly areas, due to socio-economic changes, combined with the effects of global warming, may have facilitated the spread of this species [3,13].
Similar to B. haematurus, other Bombus species (e.g., B. argillaceus, B. niveatus Kriechbaumer, B. schrencki Morawitz, and B. semenoviellus Skorikov) may also benefit from climate change and potentially expand their current ranges in Europe, even if for other bumblebee species a reduction in their distribution is reported [4,8,9,19,40,41,42,43].

5. Conclusions

The present study indicates that B. haematurus is now permanently established in FVG in northeastern Italy and that a further spread of the species towards the west, into the neighbouring Veneto region, is likely in the short term.
Bombus haematurus joins some new native species of Apoidea recently detected in Italy [44] and a few other wild bees that have reached the country in recent years, such as the megachilids Megachile sculpturalis (Smith), which has become naturalised [45] as well as Megachile disjuntiformis Cockerell [46], and the apid Xylocopa aestuans (L.) [47]. These non-native species were likely accidentally introduced through human activities rather than by autonomous migration.
In any case, further studies on the diffusion, biology, and ecology of B. haematurus and its potential impact on the environment will be necessary.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/d17080534/s1, Table S1: Bombus haematurus recorded in 22 sites of the Friuli Venezia Giulia region of northeastern Italy from 2023 to 2025. Sites: GO1–6, Gorizia district; TS1–4, Trieste district; UD01–10, Udine district; PN1,2, Pordenone district. Observations are listed chronologically for each site. Data on one worker captured at the site GO1 in June 2022 are included; Table S2: Data on 15 sites in the Friuli Venezia Giulia region of northeastern Italy where Bombus haematurus was not observed in the 2023–2025 period. For each district, sites are listed chronologically.

Author Contributions

Conceptualization, E.C. and P.Z.; Data curation, E.C., M.Q., A.V. and P.Z.; Investigation, E.C., A.V. and P.Z.; Methodology, E.C., M.Q., A.V. and P.Z.; Writing—original draft, E.C., M.Q. and P.Z.; Writing—review and editing, E.C., M.Q. and P.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

Not applicable.

Data Availability Statement

Data are contained within the article or Supplementary Material.

Acknowledgments

We thank Francesco Pavan for reviewing the first draft of the manuscript and Francesco Boscutti for confirming the identification of the plant species.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. Distribution map of the occurrence of the blood-tailed bumblebee Bombus haematurus in Europe and Asia. Occurrence of the species: yellow dots up to 2019, light orange dots 2019–2023 period, and dark orange dots 2024–2025 period. GBIF Occurrence Download. Available online: https://doi.org/10.15468/ab3s5x (accessed on 12 January 2025) [10].
Figure 1. Distribution map of the occurrence of the blood-tailed bumblebee Bombus haematurus in Europe and Asia. Occurrence of the species: yellow dots up to 2019, light orange dots 2019–2023 period, and dark orange dots 2024–2025 period. GBIF Occurrence Download. Available online: https://doi.org/10.15468/ab3s5x (accessed on 12 January 2025) [10].
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Figure 2. Distribution of Bombus haematurus in the Friuli Venezia Giulia region of northeastern Italy. Bumblebees of this species recorded during the 2023–2025 survey at 22 sites (green marks): Sites TS1–4 in the Trieste district, sites GO1–6 in the Gorizia district, sites UD1–10 in the Udine district, and sites PN1,2 in the Pordenone district. Red marks: Fifteen sites without Bombus haematurus during the 2023–2025 survey. White star: First record of Bombus haematurus for Italy in 2017 [6]. Data on one worker captured at the site GO1 in June 2022 are included (image modified from Google Earth).
Figure 2. Distribution of Bombus haematurus in the Friuli Venezia Giulia region of northeastern Italy. Bumblebees of this species recorded during the 2023–2025 survey at 22 sites (green marks): Sites TS1–4 in the Trieste district, sites GO1–6 in the Gorizia district, sites UD1–10 in the Udine district, and sites PN1,2 in the Pordenone district. Red marks: Fifteen sites without Bombus haematurus during the 2023–2025 survey. White star: First record of Bombus haematurus for Italy in 2017 [6]. Data on one worker captured at the site GO1 in June 2022 are included (image modified from Google Earth).
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Figure 3. Flight period of three castes of Bombus haematurus observed during the survey 2023–2025 in the Friuli Venezia Giulia region of northeastern Italy.
Figure 3. Flight period of three castes of Bombus haematurus observed during the survey 2023–2025 in the Friuli Venezia Giulia region of northeastern Italy.
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Figure 4. Bombus haematurus queen (left) and male (right) on Crocus heuffelianus and Lamium galeobdolon, respectively.
Figure 4. Bombus haematurus queen (left) and male (right) on Crocus heuffelianus and Lamium galeobdolon, respectively.
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Table 1. Bombus haematurus bumblebees recorded at 22 sites in the Friuli Venezia Giulia region of northeastern Italy during the survey period (2023–2025). Each site was visited on one or more sampling dates and, in the latter cases, in the same year (1y), two years (2y), or three years (3y). For each site, the total number of bumblebees, along with the counts for queens (Q), workers (W) and males (M), is reported. For each site and month, the number of bumblebees observed is indicated. When the sampling dates are more than one, their number is noted in parentheses. Sites are differently labelled based on their collocation in natural (underlined) or semi-natural areas (i.e., suburbs and rural) (no label). * Data on one worker captured at site GO1 in June 2022 are included.
Table 1. Bombus haematurus bumblebees recorded at 22 sites in the Friuli Venezia Giulia region of northeastern Italy during the survey period (2023–2025). Each site was visited on one or more sampling dates and, in the latter cases, in the same year (1y), two years (2y), or three years (3y). For each site, the total number of bumblebees, along with the counts for queens (Q), workers (W) and males (M), is reported. For each site and month, the number of bumblebees observed is indicated. When the sampling dates are more than one, their number is noted in parentheses. Sites are differently labelled based on their collocation in natural (underlined) or semi-natural areas (i.e., suburbs and rural) (no label). * Data on one worker captured at site GO1 in June 2022 are included.
DistrictGeographic AreaSitem a.s.l.N. of VisitsBombus haematurus
TotalQWMFebMarAprMayJuneJuly
GoriziaEastern Friulian plains (Isonzo plain)GO1332 *2-2----11-
GO21187; 3y266182-6 (3)6 (2)14 (2)--
GO311611-1-- -1---
GO45511-1-----1-
GO5333; 1y13364--7 (2)6--
GO6108122---2----
TriesteCoastTS1902; 2y22--1-1---
Karst plateauTS219711-1----1--
TS3128111---1----
TS4165111---1----
UdineMorainic hillsUD114216, 3y147408027-29 (5)14 (5)103 (5)1-
UD21612, 1y66---6 (2)----
UD31435, 1y651--2 (2)3 (2)-1-
UD4218144---4----
UD5147111---1----
Julian Prealps UD62102, 2y22---11---
UD7364155-----5--
Central Friulian plainsUD8642, 1y3-21---12-
UD9295, 1y10-10----45 (3)1
UD101011-1------1
PordenoneCarnic Prealps PN1135111----1---
PN224712-2-----2-
Total 57238791253415334135132
Table 2. Number of Bombus haematurus recorded per month (February–July) on flowering plant species during the 2023–2025 survey across 22 sites in the Friuli Venezia Giulia region of northeastern Italy. Plant species identified as new food resources are in bold. Nectar and pollen per plant species were evaluated using three degrees of assessment (+++, excellent; ++, good; and +, poor). The number of events refers to the total observations per plant species in the same or different sites. Data on one worker captured on Lavandula angustifolia in June 2022 are included.
Table 2. Number of Bombus haematurus recorded per month (February–July) on flowering plant species during the 2023–2025 survey across 22 sites in the Friuli Venezia Giulia region of northeastern Italy. Plant species identified as new food resources are in bold. Nectar and pollen per plant species were evaluated using three degrees of assessment (+++, excellent; ++, good; and +, poor). The number of events refers to the total observations per plant species in the same or different sites. Data on one worker captured on Lavandula angustifolia in June 2022 are included.
FamilySpeciesPlant FeaturesN. of EventsN. of Bombus haematurus
Flowering PeriodNectarPollenFebMarAprMayJuneJulyTot.
BoraginaceaeEchium vulgare L.IV–IX+++++4, 1 site---44-8
CaprifoliaceaeKnautia drymeia Heuff.V–VII++ (*)++ (*)2, 1 site---11-2
LamiaceaeLamium galeobdolon (L.)IV–VIII+++11, 4 sites--61012-109
Lamium maculatum L.III–XII+++12, 5 sites-313131-30
Lamium orvala L.III–VI+++11, 7 sites-51071-23
Lamium purpureum L.III–X+++6, 5 sites-13----13
Lavandula angustifolia Mill.VI–IX++++3, 3 sites----123
Salvia pratensis L.V–III++ (*)NR1---8--8
Salvia verticillata L.VI–VII++ (*)NR1----1-1
Teucrium fruticans L.IV–VIII+++1--1---1
FabaceaeVicia cracca L.V–VIII++2, 2 sites---11-2
OrobanchaceaeLathraea squamaria L.III–VINRNR3, 2 sites-31---4
PapaveraceaeCorydalis cava (L.)III–V+++3, 1 site-16----16
PlantaginaceaeVeronica persica Poir.I–XII++1-1----1
RubiaceaeAsperula taurina L.III–VI+ (*)+ (*)1--1---1
IridaceaeCrocus heuffelianus Herb.II–IV+++1-1----1
LiliaceaeErythronium dens-canis L.III–IVNRNR1-1----1
RanunculaceaeHelleborus odorus Waldst. & Kit.II–IV++++2, 1 site-2----1
AsparagaceaeScilla bifolia L.III–IV+++1-1----1
Aphid (Hemiptera: Aphidoidea) honeydew on leaves of apple trees1---1--1
Flying above ground 6, 3 sites152---8
N. of Bombus haematurus 15334136122238
(*) Data reported at genus level; NR—Not reported in the literature.
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Cargnus, E.; Quaranta, M.; Villani, A.; Zandigiacomo, P. Spread and Ecology of the Bumblebee Bombus haematurus (Hymenoptera: Apidae) in Northeastern Italy. Diversity 2025, 17, 534. https://doi.org/10.3390/d17080534

AMA Style

Cargnus E, Quaranta M, Villani A, Zandigiacomo P. Spread and Ecology of the Bumblebee Bombus haematurus (Hymenoptera: Apidae) in Northeastern Italy. Diversity. 2025; 17(8):534. https://doi.org/10.3390/d17080534

Chicago/Turabian Style

Cargnus, Elena, Marino Quaranta, Alberto Villani, and Pietro Zandigiacomo. 2025. "Spread and Ecology of the Bumblebee Bombus haematurus (Hymenoptera: Apidae) in Northeastern Italy" Diversity 17, no. 8: 534. https://doi.org/10.3390/d17080534

APA Style

Cargnus, E., Quaranta, M., Villani, A., & Zandigiacomo, P. (2025). Spread and Ecology of the Bumblebee Bombus haematurus (Hymenoptera: Apidae) in Northeastern Italy. Diversity, 17(8), 534. https://doi.org/10.3390/d17080534

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