A lot of conservation and ecology seems to consist of reminding people about all the things that are dying and how awful it is. And while this is really important to act on right now, sometimes it’s nice to reflect that it’s not all doom and gloom.
The ivy bee, Colletes hederae, is one of my favourite examples of an insect that is actually doing rather well. In fact, they’ve enjoyed an almost meteoric rise in the southern UK ecology. In 1990, they weren’t even a known species – C. hederae was only described as a new species distinct from the related C. halophilus (which prefers sea aster) and C. succinatus (which visits various things but especially heather) in 1993. More information about their key differences has appeared even more recently1.
They first appeared in the UK in 2001, a similar time to the harlequin ladybird (2004; a rather less welcome invasion) and the tree bumblebee (2001; seem to be fitting into the ecology fairly seamlessly so far), but seem to have really boomed in the last 5 years or so.
To me, they are a sign that autumn is here, but one of the more cheerful aspects of autumn. Their phenology is well-timed to coincide with the ivy flowering, and for a few weeks of frantic activity, they appear almost from nowhere. We have just come to the end of their annual period of activity; such is their local success in Medway that almost any flowering ivy around here seemed to have at least a few and possibly lots. Stand underneath a particularly large, well-visited plant and you found yourself in a gently-humming rain of knocked-off anthers and pollen. That said, apparently they don’t limit themselves exclusively to ivy, so if their timing is a little bit off you probably don’t need to worry too much: they’ve also been recorded using various yellow Asteraceae, clover, medick, goldenrod and autumn crocus3 – though we’re not sure how well the larvae do on non-ivy pollen.
Around here in Kent, they seem to have some nesting preferences: they like to nest in well-drained banks, preferably south facing or at least sunny, with light soil and a decent bit of threadbare grass. Less manicured lawns, churchyards and some sloping road verges seem quite good. When they’ve found a place they like, the numbers can get quite enormous; we walked down a street for about 300m and almost every front garden was, in mid-September, “swarming” with them. The busy-ness is usually mostly the males patrolling the site for virgin females emerging, along with females trying to nest and avoid the harrassment, and frequent dramatic “mating balls” as multiple males pounce on a female and roll down the bank in a cluster. Apparently a species of blister beetle has “hijacked” this phenomenon – they release very similar pheromones and as a result, the poor, desperate ivy bee males attempt pseudocopulation with the young larvae of the beetle, Stenoria analis, resulting in the tiny beetle larvae getting stuck to the bees and carried off, so they can go on to become nest parasites of the ivy bees3.
They’re fascinating to watch, not least because they’re harmless – you can stand right next to one of these “swarming” banks without concern, with bees bouncing off your trousers, and just enjoy the spectacle. And as a figurehead for solitary bees, they certainly are photogenic, with their cute furry faces and striking markings.
I suppose they’re doing something nice for the wider ecology, too. While wasps and bumblebees are also ivy pollinators, this level of activity must surely increase ivy fruit-set, leading to more berries over winter, which I’m sure the birds appreciate. I don’t have any evidence, but perhaps our ivy bees are also doing our overwintering birds a favour?
While Britain may not enjoy spectacular mass phenomena like the Monarch butterfly migration, perhaps we should rebrand the impressive coming of the ivy bees as our symbol of early autumn.
BWARS have been tracking the spread of ivy bees for the last few years, so records from future years can be recorded here.
1Kuhlmann, M., Else, G. R., Dawson, A., & Quicke, D. L. (2007). Molecular, biogeographical and phenological evidence for the existence of three western European sibling species in the Colletes succinctus group (Hymenoptera: Apidae). Organisms Diversity & Evolution, 7(2), 155-165.
2Westrich, P. (2008). Flexibles Pollensammelverhalten der ansonsten streng oligolektischen Seidenbiene Colletes hederae Schmidt & Westrich (Hymenoptera: Apidae). Eucera, 1(2), 17-29.
3Vereecken, N. J., & Mahé, G. (2007). Larval aggregations of the blister beetle Stenoria analis (Schaum) (Coleoptera: Meloidae) sexually deceive patrolling males of their host, the solitary bee Colletes hederae Schmidt & Westrich (Hymenoptera: Colletidae). Annales de la Société entomologique de France 43(4), 493-496.