Monitoring of Hymenoptera in Prague - Project with the City Hall 2024-2025

Hymenoptera Monitoring in Prague for the City Hall 2024 - 2025

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What you will learn here

About the project
How the project went
How did it turn out?
What are we planning next?

Last updated: 9/2/2026

Thanks

This project was created with the financial support of the Prague City Hall as part of the environmental grant program.

We would also like to thank many other people who supported us during the preparation of the project and who provided us with many valuable recommendations and suggestions.

For Čmeláci PLUS zs.

O. Herzog

Bumblebees in Prague – Hymenoptera Monitoring 2024-2025
Photo: O. Kahoun

About the project – Introduction

We thought about this project for a long time. Finally, we gathered the courage and went ahead.

Prague is very interesting and, unlike the surrounding agricultural landscape, there is less chemistry and more opportunities.

In many places, our members and friends have found many interesting species of bumblebees. They have mostly disappeared, but the desire to find them is great. Moreover, no systematic data collection on hymenoptera is carried out in Prague.

That's why we met with a specialist in the care of protected areas from the CITY OF PRAGUE and, after consulting with them and the Czech University of Life Sciences, prepared this project.

The project was created with the financial support of the Prague City Hall as part of the environmental grant program.

Default state

A number of professional studies point to a global negative trend – a significant decline in insects. This concerns both the number of insects and the number of species. The decline in species diversity is described in the order of tens of percent. Some peer-reviewed studies point to a loss of even 70-80% of individuals.

Insects are one of the key groups for the functioning of all ecosystems. Rapid declines, especially their continuing trends, are alarming. That is why this problem has recently received a lot of attention from both the professional and lay public. This topic is covered in the media - often, attention is inappropriately focused only on the honey bee (Apis mellifera) and its importance is overestimated, to the detriment of other pollinators from the insect kingdom.

The species diversity and abundance of insects are negatively affected by a number of factors. They do not act in isolation, but are interconnected, which is why there is no simple solution to such a situation. The main causes of insect decline include the loss of suitable habitats, the intensification of agriculture and forestry, the ever-increasing chemicalization of the environment, etc. In cities, there is continuing urbanization and a number of other civilization pressures, including human movement in nature, often regardless of the level of protection of the given place. Many insect species are endangered in some way, and an analysis of the species richness of insects in the Czech Republic has shown that the unfavorable situation also affects us.

The capital city of Prague is an exception. Sometimes Prague is referred to as a European phenomenon, due to the diversity of some insect species. However, since biodiversity is often concentrated in small, unconnected areas, this situation can change quickly. It is not only about the isolation of such areas, but also about the negative effects of intensive farming in the common agricultural landscape that borders such places. Species-diverse insect habitats are further attacked by housing construction and also by expanding infrastructure. This leads to further fragmentation of such places, up to their practical disappearance. Civilization pressure is also intensified by inappropriate grass management of public areas. Places that could be used by insects are maintained only with regard to human needs, resulting in lifeless green areas.

Many suitable habitats on the outskirts of cities are disappearing, along with many natural pollinators. What is very dangerous is that everything is happening mostly secretly.

Society is acutely aware of the decline of insects. In addition to the honey bee, the general public also positively perceives representatives of the Hymenoptera (Hymenoptera), especially from the Apidae family – specifically bumblebees (Bombini). They are perceived as friendly, social insects. At the same time, they also serve as an important bioindicator of the state of nature. However, they are also affected by all the negative factors mentioned above, and their populations are shrinking and species are disappearing.

An example of the disappearance of a once relatively abundant bumblebee species is the striped bumblebee (Bombus subterraneus). It used to occur in several places in Prague, but has not been detected there for several years. Another species that is declining is the inconspicuous eel bumblebee (Bombus ruderarius). The decline of these specific species is known only to the professional community.

Systematic monitoring of hymenoptera insects is not carried out, data for monitoring trends is lacking, and rare species are declining secretly and without public attention.

Similarly, monitoring of hornets (Vespidae) is not carried out. Some of their species are endangered, and are also unjustifiably classified as “insects dangerous to humans”. In the case of hornets, the media has also raised concerns about invasive “Asian” species. This may, for example, lead to the elimination of populations of the common hornet (Vespa crabro).

The importance of hornets (Vespidae) has long been underestimated. As predators, they primarily hunt the most available insects at a given moment. They are thus able to suppress and regulate even overgrown pests from the flying insect family, as well as insectivorous birds and bats.

Inappropriate care of public grass areas often leads to degradation of such places. Public green space managers are often unaware that by systematically mowing the lands entrusted to them, they indirectly contribute to the decline of pollinators.

If data are lacking to document insect declines in specific locations, habitats suitable for natural pollinators cannot be sufficiently protected and specific remedial solutions cannot be systematically developed. However, targeted measures could be developed to protect specific insect species and suitable habitats.

Project team

Implementation team:
Čmeláci PLUS zs – Ondřej Hercog, Jaromír Čížek, Luděk Šulda, Jakub Černý, Ondřej Hercog
External cooperation: Mgr. Jakub Straka, Ph.D.

Bumblebees in Prague – Hymenoptera Monitoring 2024-2025
Photo: O. Kahoun

Project objectives and their fulfillment

The aim of the project was to map the species diversity of selected groups of Hymenoptera insects, primarily bumblebees, and to identify locations that would deserve special protection.

C1 – Create a list of habitats where rarer species of bumblebees (Bombini) occur

C2 – Ensure the collection of basic data on the diversity and abundance of bumblebees (Bombini) and hornets (Vespiade) in the territory of Prague

C3 – Provide data usable for modifying measures and data for the care of open countryside in Prague in general

C4 – Provide monitoring data for further processing and follow-up projects

C5 – Media coverage of the project and its results

Project preparation

The project was launched in May 2024, prior to grant approval. Bumblebee phenology is time-limited, so we started the preparatory work in good time.

First, the project team selected 27 locations in Prague. These were proposed locations where members of the ČM+ Association had previously detected interesting bumblebee species.

The proposal was subsequently consulted with specialists from the Environmental Protection Department of the Greenery Care Department. The following documents from the City of Prague were also used in the selection:

Source: Prague Nature

Source: Prague Meadows and Steppes | Prague Nature

The result was a final list of 27 locations:

Source Map of sites and transects

Most of the transects are located 3 km apart, which is the theoretical flight distance of bumblebees. The transects are therefore interconnected.

Fieldwork (2024-2025)

The actual monitoring took place at selected locations, transects T1 -T27.

Data collection was started ahead of schedule on 31/5/2024. Based on the experience gained, we corrected the procedures and forms. We used these in further data collection.

Each transect was walked slowly by a surveyor during the visit. Individuals were monitored primarily on nectar-producing plants that provide sustenance for the monitored insects. Data collection also took place in the immediate vicinity of the transect.

During the mission, the mapper carefully captured, identified, and recorded all individuals of selected groups of Hymenoptera that he observed. The captured insects were released back into the wild immediately after identification on site.

In the case of unclear determination, individual individuals were documented for later determination by an external specialist.

The mappers worked carefully to avoid harming any of the observed individuals. This accuracy of determination was sufficient for our purposes.

In several cases, we used the presence of bumblebees to infer the presence of certain bumblebee species. Bumblebees of a given species primarily host certain specific bumblebee species.

For example, the hairy bumblebee ( Bombus barbutellus ) hosts B. hortorum, B. ruderatus, and B. argillaceus.

Monitoring was carried out under the above-mentioned standardized conditions.

For each transect, the following were recorded:

species of bumblebees and hornets,
number of individuals and their caste (mother, worker, male),
date and time of monitoring,
climatic conditions,
nectar-bearing plants present,
brief description of the habitat

Nectar-bearing plants in flower were recorded – on the transect and in its immediate vicinity. When recording plant species, we focused on nectar-bearing plants where we observed bumblebees or which are popular with them.

The data was then transcribed into a structured database (XLS). This database is part of the project documentation.

Where necessary, we also collected photo documentation. The photos are only in documentary quality.

Bumblebees in Prague – Hymenoptera Monitoring 2024-2025
Photo: O. Kahoun

Data processing

The first data processing took place in October - November 2024. The main part of the data collection took place in 2025.

The data were further analyzed in 2025. However, we must admit that we underestimated our estimate of the time required for the project. We did not want to just hand over bare data, but to share our experiences and, where possible, provide specific suggestions for specific transects.

Determination of problematic species

In 2024, no problematic species were detected, external determination was not used. We used the support of an external worker in 2025.

Bumblebees in Prague – Hymenoptera Monitoring 2024-2025
Photo: O. Kahoun

Evaluation of the fulfillment of individual goals

C1 – Create a list of habitats where rarer species of bumblebees (Bombini) occur – COMPLETED

C2 – Ensure the collection of basic data on the diversity and abundance of bumblebees (Bombini) and hornets (Vespiade) in the territory of Prague – COMPLETED

C3 – Provide data usable for modifying measures and data for the care of open countryside in Prague in general – COMPLETED

C4 – Provide monitoring data for further processing and follow-up projects – COMPLETED

C5 – Media coverage of the project and its results – COMPLETED

Bumblebees in Prague – Hymenoptera Monitoring 2024-2025
Photo: O. Kahoun

Summary reports and comments

We have compiled the following summary reports from the data obtained.

Due to the small number of collections, it does not make sense to process the data statistically, as they are burdened by a relatively large systematic error and the influence of external conditions.

Nevertheless, they can provide answers to some basic questions .

The data can be further analyzed , our questions are just an example.

Bumblebees PLUS - Monitoring of Hymenoptera in Prague 2024 - 2025 - Photo Ondřej Kahoun

Monitoring of Hymenoptera in Prague 2024 – 2025
Photo: O. Kahoun

Bumblebees (Bombini) summary

1. What was the distribution of bumblebee species across all 27 transects?

From the summary graph, it can be confirmed that this is essentially a typical distribution of bumblebee species according to abundance across the Czech Republic (except for specific localities).

The distribution of patchouli species corresponds to this as well - according to the frequency of their host species.

Further processing can provide overviews of individual transects, but they will be very similar. We will leave this as an activity outside the project.

2. What was the species diversity of bumblebees on individual transects?

The following graph clearly shows the differences between the individual transects:

Best transects by number of species

· T18 12 species of bumblebees on Vidoula

· T10 Prokopské Valley 12 species of bumblebees

Worst transects by number of species

· T15 Troja – 4 species of bumblebees at the press

These differences did not surprise us. The influence here is the amount of data, but of course the local conditions on the transects. The favorite T10 Prokopské údolí confirmed its role. The dry transect T15 in Troja did not surprise.

3. Is there a relationship between the species diversity of nectar-bearing plants?

Our data collection did not confirm such a dependence. This is due to the amount of data obtained and other influences. Some bumblebee species are able to fly longer distances, others prefer a shorter distance between the nest and the food source. From our previous observations, we believe that some rare bumblebee species with rapid nest development prefer a shorter distance between the food source and the nest site. We do not have hard data for our observation.

Although we collected data on nectar-bearing plants, we ultimately did not use this information in the processing. If more detailed data on the species diversity of nectar-bearing plants are available, it is possible to subsequently link them with our data.

Example

T18 On Vidouli 12 species of bumblebees 17 species of nectar-producing plants
T10 Prokopské údolí 12 species of bumblebees 14 species of nectar-producing plants

versus

T15 Troja – At the press 4 species of bumblebees 12 species of nectar-producing plants
T21 Coltsfoot 5 species of bumblebees 12 species of nectar-producing plants
T26 Botič and Vinný potok 5 species of bumblebees 17 species of nectar-bearing plants

Likewise, we did not include data on nesting opportunities, which vary from bumblebee species to species, in our data collection.

4. Were rare species detected during data collection?

For our processing, we have prepared the following table. It consists of most species described in the Czech Republic, an assessment of abundance (there is no current source available here, due to the dynamics of changes, among other things, we used our view of abundance in Prague and the surrounding area) and the Red List of Threatened Species - 2017.

The rows marked in green represent the species we detected as part of the project.

The most interesting find from our collection is the eel bumblebee (B. ruderarius). Unfortunately, we did not find species that were previously relatively abundant in some localities and transects. These include species such as the striped bumblebee (B. subterraneus) and the humen bumblebee (B. ruderatus).

We also did not find a species that was detected in the urban environment of České Budějovice, the deceptive bumblebee (B. confusus).

We did not expect other species of rare bumblebees, so their absence did not surprise us.

Rare species of bumblebees

Long-haired patchouli (B. barbutellus)

Finding: T10 Prokopské údolí, T18 Na Vidouli
This bumblebee typically hosts B. hortorum, B. ruderatus, and B. argillaceus , so it can be used as an indication of which species is present. Bumblebees of a given species primarily host certain bumblebee species.

Source: https://en.wikipedia.org/wiki/Bombus_barbutellus

Less abundant bumblebee species

We used the same mapping table

a) Less abundant species

Bumblebee (B. ruderarius)

T16, T18, T19
This bumblebee is not yet listed in the "Red Book", but the trend of decline in its population is alarming.

b) Moderately abundant species

Wood bumblebee (B. sylvarum)

T1, T2, T3, T4, T5, T7, T8, T9, T10, T11, T12, T16, T17, T18, T19, T20, T24, T25, T27

Bumblebee (B. humilis)

T1, T2, T5, T7, T8, T10, T11, T18, T19, T20, T22, T23, T25, T27

Bohemian patchouli (B. bohemicus)

T8, T9, T10, T16, T17, T20, T23

Wild patchouli (B. sylvestris)

T10, T17

5. Why were the numbers of hypnotic bumblebees (Bombus hypnorum) recorded low?

The low number of B. hypnorum records in the monitoring is mainly due to the fact that the survey was carried out in habitats that are not suitable for this species. The monitoring was mainly focused on meadow areas and strips of woodlice, i.e. environments where B. hypnorum does not commonly occur. This species prefers forest edges, clearings and shrubbery, often near fruit trees (e.g. gooseberry, apple tree), which were not part of the monitored routes.

Individuals observed during field data collection appeared, for example, on the swallowtail in stands near Botič, which are forest clearings with limited accessibility. It can be assumed that the occurrence would be significantly higher in these types of habitats, similar to B. lucorum, which shares similar preferences.

Another factor is early spring, when the majority of the population is made up of searching mothers. They move high in the air and are practically undetectable on the ground, which further reduces the chance of recording them during standard monitoring.

We believe that the B. hypnorum population is being attacked by a number of parasites that are increasingly weakening their populations. Data collection may also have been affected by the fact that this species is early and its cycle ends relatively early, our data collection may have missed it.

Commentary – Coexisting species

From our previous experience, for example, B. subterraneus and B. ruderatus were abundant on T3, accompanied by B. hortorum, B. sylvarum, and B. ruderarius.

Recommendations for landscape care

Where possible, we have provided specific recommendations for changes to the care plan. These can be generalized, discussed with botanists, and further utilized.

As part of the processing, evaluation and interpretation of the results, we wanted to recommend supporting white nightshade (Lamium album), which is an important food source for Bombini - especially for rare species such as B. subterraneus.

In light of the previous text, we do not want to map the absence of such species to the absence or weak population of the white-bellied toad. However, our recommendation across transects is to support this nectar-producing plant.

During consultations with botanists from the Czech University of Life Sciences, we surprisingly discovered that no one is interested in this "uninteresting flower".

We hereby present a proposal based on our experience and practice. This or a similar solution could be included in the care plan.

Support for white ragwort (Lamium album) – proposal

White sedge is not a species of stable meadows or long-term maintained grasslands. It belongs to early successional habitats, where soil disturbance and nutrient supply occur regularly. To maintain itself, it needs cyclically renewed conditions – similar to the semi-natural pastures with trees, where we traditionally see it.

Understanding environmental requirements

White cowslip germinates and thrives where there is disturbed turf, plenty of light, moisture, and a higher nitrogen content.
Without disturbance, the vegetation quickly grows and the sedge disappears.
Its life cycle is short, so it does not form a stable, permanent growth like clover or meadow herbs.

How to create suitable conditions

A. Disturbance (key step)

Mechanical disturbance of the turf (digging, dragging, tearing off the turf).
Intensive short-term trampling (e.g. temporary release of animals).
Local fertilization with organic matter (compost, manure, litter).
Disturbance should occur repeatedly, at least once every few years.
Follow-up care after germination

B. Suitable cutting

1–2 mowings per year.
Do not mow too low to avoid damaging young plants.
Leave/replenish some biomass in place to replenish nutrients.
Inspiration from semi-natural pastures

C. The “pasture with trees” model

In the summer, animals trample the turf, adding nutrients and eating the lower branches of trees.
In the fall, when animals move elsewhere, space is created for the germination of earwigs.
Both white and purple hyacinths can handle the summer heat.

Recommended care cycle

Year 1: Disturbance + nutrient supply.
Years 2–4: 1–2 mowings per year.
Year 5: The growth thickens.
Year 6: Repeat disturbance.

Summary

White cowslip will only survive where there is regular disturbance, sufficient nitrogen, enough light, and limited competition from grasses.
The only way to provide long-term support is to repeat the cycle of disturbance and subsequent gentle care.

Bumblebees in Prague – Hymenoptera Monitoring 2024-2025
Photo: O. Kahoun

Conclusion

The project fulfilled all of its set goals and confirmed that systematic monitoring of selected groups of hymenoptera insects in the Prague area is important for their protection and for landscape care planning.

An overview of 27 transects across the territory of Prague was created. A total of 15 bumblebee species were detected out of a total of 41 that have been described in the Czech Republic. Basic data on the diversity and abundance of bumblebees (Bombini) and partly also hornets (Vespidae) were collected. The project provided data that can be used for the management of greenery and open landscapes.

The project also included a simple analysis and interpretation of the obtained data. Although the scope of the obtained data does not allow for statistically representative conclusions, we managed to identify key localities, draw attention to the occurrence of less abundant or endangered species and point out differences between individual transects. The results are fully usable for further processing - whether in the form of follow-up projects, extended monitoring or deeper ecological analysis.

The expected benefits of the project have been realized. We have a comprehensive set of data, practical recommendations for landscape care, and specific suggestions for adjusting management at selected locations.

The project also contributed to raising awareness of the issue of insect decline and the importance of pollinators in the urban environment. This communication will continue in the form of lectures, professional meetings, cooperation with the Prague City Hall, as well as directly with individual city districts and departments responsible for green management.

The knowledge gained represents the basis for further steps in protecting biodiversity in Prague.

The project showed that even relatively simple monitoring can provide valuable information and become an impetus for longer-term and more systematic care for natural pollinators and their habitats.

We are ready to follow up on this project with partial activities and projects. One of them could be, for example, the reintroduction of rare species of bumblebees to places where they used to thrive. Such places still exist thanks to the work of the Prague City Hall.