Ivy bee event goes ahead smoothly shock

Ivy League event 25 Sept 2016

Sometimes organising a wildlife-spotting event is a tense matter of hope and prayer that the featured species will actually turn up.

No such problems yesterday, luckily dodging the showers, for a warm blue-skied autumn afternoon looking for the Ivy bee Colletes hederae, with colleagues from Exmouth Local Group.  

This handsome solitary bee was busy in numbers, swarming at ankle height round the coastal grasslands of the Maer, and the mini-quarries of bare earth where it excavates its nests. Faster than the eye can follow, only when stopped for some digging were there chances for a good view, and non-blurred photos.

Head in the sand - busy burrowing out a nest site

Not recognised as a separate species until 1993 (from the similar C. halophilus and C. succinctus), and first sighted in the UK in Dorset and at a single location in Devon in 2001, it has gradually been spreading its range since. Ivy Hedera helix , which flowers late in the year, is its predominant, and often sole, pollen and nectar source of choice; hence, in sync, the Ivy bee is also late flying; in more sense than one, it's our latest solitary bee.

Although solitary, where the habitat is suitable, as it definitely is at the Maer, large numbers can nest in aggregations, a fascinating, often overlooked, spectacle, right under one's feet.

Potted (natural) history: Ivy bee reveals itself to budding naturalist

From the nesting site on to the other main component of the life cycle, stopping off to check out a dense clump of ivy. Ivy bees were conspicuous foraging here, alongside numerous other bees, wasps, hoverflies and other insects, at this important late food source. A successful event, which the wildlife also turned up to.

Eristalis hoverfly (note looped vein in wing)

Some further information about the Ivy bee:

• BWARS webpage and info sheet 
• National mapping project
• Video of the amazing 'mate balling' behaviour taken in east Devon

Knotgrass in my backyard

Life after concrete (reprise)

Knotgrass Polygonum aviculare 
The sort of plant which catches the attention of herbicides, in the name of botanical cleanliness. But Wait! Stop before you spray!   

Not just a weed, this is a bare ground coloniser, taking nature's first steps to fill a vacuum. It has noted wildlife value: as the 'aviculare' part of the name suggests, birds such as finches and sparrows feed avidly on the seeds. 

Knot overlooked ... supporting wildlife on Cathedral Green

Added to which, the long flowering period can support insects from May - November. Right now Knotgrass clumps are flowering in profusion around Cathedral Green and St David's church, in the worn bare areas among the grass. 

The tiny clusters of 1-6 flowers emerge at the bases of the upper leaf stalks. The three inner stamens are bent over so that pollen falls directly on the styles; the others point outwards for any passing insects. But this isn't all: there are also concealed flowers under the membraneous sheaths (the ochreae) around the stem 'joints' (the joints give the plant the other part of its scientific name: Polygonum 'many - kneed'). These hermetically sealed flowers do not open (or in technical terminology, are cleistogamic), which, along with the arrangement of inner stamens, ensures some self-pollination at least. It is said Knotgrass may produce similar cleistogamic subterranean flowers underground as well, among its roots and runners, alongside which the tap root can penetrate up to 45cm deep into the ground. 

As a multi-pronged pollination and propagation strategy, these would be useful adaptations for an annual plant, which dies off every year, but for which the seed bank must persist biding its time in the soil for years, until the next unpredictable opportunity brings seeds to the surface where they can expeditiously germinate.

As well as a pioneer species to kickstart vegetation recovery on bare ground, Knotgrass is a host plant for over a hundred different invertebrates: some 9 beetle species, 2 flies, 8 bugs, and 93 moths, especially among the the Geometer moths.  

Tolerating a bit of Knotgrass in the bare patches and nooks and crannies among the concrete would be small, simple and effective action to help our urban wildlife.