Colletes hederae: The new bee in town

At first glance, a city is a hodgepodge of buildings, busy streets and public squares, people, traffic, and overall bustle. Yet, if you manage to see past the cacophony of everyday life, there is so much more to explore. A small co-resident of many cities, the ivy bee, reminds us of this.

Colletes hederae, more commonly known as the ivy bee is a relatively newly described species as it was discovered only in 1993 (Schmidt and Westrich 1993). It is a plasterer bee, meaning that they will make their nests by burrowing into the ground up to a depth of approximately 60 cm where separate cells, reinforced with saliva, are made in which the eggs are laid with the subsequent pollen and nectar as a snack for the larvae (Bischoff et al., 2005). Like many of its close family members, it has a solitary lifestyle, although they do tend to aggregate their nests quite closely together, with up to 300 nests per square meter (Hennessy et al., 2021)! The ivy bee, contrary to many other bees, prefers autumn and can be found flying around from early September until November (Roberts & Vereecken, 2010). This is also precisely the time in which the Hedera helix, to which this bee owes its name, is flowering. It is then also no surprise that it mainly uses the pollen of this ivy to look after her offspring.

The English ivy is a very common plant that can be found in high abundance from Western to Southern and Central Europe (Korszun & Bykowska, 2012). It is especially popular in cities because it is a plant that can climb quite easily, making it a useful species for green facades in cities. These facades are vertical greenery systems that help combat multiple problems commonly faced in cities, such as reducing the urban heat island effect. This is because the albedo, which is a measure of how much sunlight a material is able to reflect, of plants is lower than that of concrete which means that these will not heat up as much, resulting in a cooler city (Price et al., 2015). One of the easiest and most cost-efficient ways of accomplishing this is by using a quick climbing species, like Hedera helix that is not too picky when it comes to the environmental conditions to which it is exposed (Hudson, 2022). The ivy is able to withstand seasonal drought very well and can grow in both light and shade conditions (Metcalfe, 2005).

On the other hand, the emergence of the ivy in cities is controversial. For example, the municipality of Amsterdam recently granted new permits that allow for facades of even some monumental buildings to be covered by plants, such as ivy. This resistance arose because it would take away the view of these buildings as well as structurally weaken them (RTL, 2023). Furthermore, the ivy is often thought to strangle other trees with its vines but little empirical evidence exists to support this claim (Metcalfe, 2005). Despite the ongoing debate, given how prevalent ivy is in most cities it is clear which side is winning.

The journey of the ivy bee is quite spectacular. In the years after its discovery, it has managed to spread quite rapidly over a large part of Europe in a mainly northwestern direction (Bogusch et al., 2021). Where it once mainly occurred in Croatia, Italy, and France, it can now be found from The Netherlands and the UK to Slovenia and Slovakia and has basically extended its range across the entirety of Western Europe (Bogusch et al., 2021). The direction of this movement is especially clear in England, where it has managed to spread in only 20 years from the southern city of Dorset all the way to Scotland and Ireland (Carreck et al., 2023). However, what has facilitated the ivy bee to expand its geological range to the northern part of Europe? The answer to this question can most likely be found in cities. This is partly because as mentioned before the abundance of its host plant the ivy is quite high in cities. Furthermore, the ivy bee prefers higher temperatures and it has been suggested that the increased temperatures during summer and autumn have sped up the expansion of the ivy bee (Dellicour et al., 2013). Given that cities in general are warmer than the surrounding areas, it is quite logical why these bees seem to prefer cities.

Where there are species, there are parasites and this case is no different. Due to the ability of Colletes hederae to sail to unknown territories, it allowed Stenoria analis to follow suit. The common name of this species is the ivy bee blister beetle which uses quite an ingenuine system to exploit the ivy bee. It turns out that larval aggregations of this blister beetle to male ivy bees smell like females. However, when these unsuspecting males land, they will merely find the larvae that will then latch onto the male. During mating of the bees, the larvae will then once again hop over after which they will be exported to the burrow where the female bee intends to deposit her eggs. Unfortunately for her, the only ones that will survive are the new generation of blister beetles (Vereecken & Mahé, 2007).

As we have seen, there is much more to cities than meets the eye. Therefore, the next time you are in a city, I urge you to take a keen look around as you might find something special on the next corner!

 

References:

Bischoff, I., Eckelt, E., Kuhlmann, M. (2005) On the Biology of the lvy-Bee Colletes hederae Schmidt & Westrich, 1993 (Hymenoptera, Apidae ) – Bonn zoological Bulletin – früher Bonner Zoologische Beiträge. – 53: 27 – 36.

Bogusch, P., Lukáš, J., Šlachta, M., Straka, J., Šima, P., Erhart, J., & Přidal, A. (2021). The spread of Colletes hederae Schmidt & Westrich, 1993 continues – first records of this plasterer bee species from Slovakia and the Czech Republic. Biodiversity Data Jurnal, 9. https://doi.org/10.3897/bdj.9.e66112

Carreck, N.L., Andernach, J., Ariss, A., Dowd, H., Gant, A., Garbuzov, M., Hennessy, G., Nash, L.,Stagg, A., Ratnieks, F.L.W. (2023) Distribution and abundance of the ivy bee, Colletes hederae Schmidt & Westrich, 1993, in Sussex, southern England. BioInvasions Records 12(3): 681–697, https://doi.org/10.3391/bir.2023.12.3.06

Dellicour, S., Mardulyn, P., Hardy, O. J., Hardy, C. M., Roberts, S. P. M., & Vereecken, N. J. (2013). Inferring the mode of colonization of the rapid range expansion of a solitary bee from multilocus DNA sequence variation. Journal Of Evolutionary Biology, 27(1), 116–132. https://doi.org/10.1111/jeb.12280

Hennessy, G., Uthoff, C., Abbas, S., Quaradeghini, S. C., Stokes, E. J., Goulson, D., & Ratnieks, F. L. W. (2021). Phenology of the specialist bee Colletes hederae and its dependence on Hedera helix L. in comparison to a generalist, Apis mellifera. Anthropod-plant Interactions, 15(2), 183–195. https://doi.org/10.1007/s11829-021-09807-7

Hudson, G. (2022, 13 September). Why English ivy is so valuable for city homes and public spaces. Evening Standard. https://www.standard.co.uk/homesandproperty/gardening/english-ivy-cities-pollutants-building-temperatures-wildlife-b1025125.html

RTL nieuws. Klimop: vloek of zegen? “Zonde van monumentale panden”. (2023, 9 november). RTL.nl. https://www.rtl.nl/editienl/artikel/5417929/klimop-schadelijk-monumentale-panden-amsterdam-discussie-klimplant-schade?redirect=rtlnieuws

Korszun, S., & Bykowska, J. (2012). Flowering plants of Hedera helix L. in the Grunwald district of the city of Poznań. Acta Agrobotanica, 64(1), 45–56. https://doi.org/10.5586/aa.2011.006

Metcalfe, D. J. (2005). Hedera helix L. Journal of Ecology, 93(3), 632–648. http://www.jstor.org/stable/3599428

Price, A., Jones, E. C., & Jefferson, F. (2015). Vertical Greenery Systems as a Strategy in Urban Heat Island Mitigation. Water, Air And Soil Pollution/Water, Air & Soil Pollution, 226(8). https://doi.org/10.1007/s11270-015-2464-9

Roberts, S., & Vereecken, N. (2010). Information Sheet IVY BEE (Colletes hederae). BWARS. https://bwars.com/sites/default/files/info_sheets/01_Colletes_hederae_20100908.pdf

Schmidt, K., & Westrich, P. (1993) Colletes hederae n. sp., eine bisher unerkannte, auf Efeu (Hedera) spezialisierte Bienenart (Hymenoptera: Apoidea). Entomol Z 103:89–112.

Vereecken, N. J., & Mahé, G. (2007). Larval aggregations of the blister beetleStenoria analis(Schaum) (Coleoptera: Meloidae) sexually deceive patrolling males of their host, the solitary beeColletes hederaeSchmidt & Westrich (Hymenoptera: Colletidae). Annales de La Société Entomologique de France/Annales de La Société Entomologique de France, 43(4), 493–496. https://doi.org/10.1080/00379271.2007.10697538