A native pollinator explores an alien flower

These sand dunes, between Alnmouth and Warkworth, have long been a favourite destination for botanists. The hollows are filled with wild thyme, biting stonecrop, bird's foot trefoil, viper's bugloss and spotted, twayblade and pyramidal orchids, to name but a few. This is also one of the only places in our region where sea pea has been recorded - which I've searched for here but never found. But when we were there a couple of weeks ago, we did come across an interesting alien.

Our visit coincided with a mass emergence of five-spot burnet moths and when they were not busy producing the next generation they were swarming all over the flowers, notably ...

...... this garden iris, possibly Iris sibirica which someone must have planted here. Bearded iris, I. germanica, is recorded as an introduced alien here in George Swan's Flora of Northumberland, but this clearly isn't a bearded iris, which has a beard of hairs in the 'gullet' of the flower . It must have been here for quite a while and bore a couple of large, empty seed capsules from last year's flowers, so might seed itself around and establish a population. 

What was mos striking about the plant was what a magnet it was for the five-spot burnets. The plant is a bit of a beacon, being the tallest brightly-coloured object in the dunes, and they homed in on it from all around.

When they landed none of the moths seemed to have any idea how to feed on the plant's nectar, but they quite quickly worked out how to reach it.

Usually, like this one and the one below, they began by probing the petal surface with their proboscis ....

..

.... then, when they found that unrewarding, moved down to the petal base to reach the nectar.....

.... but after a while most seemed to align themselves with the yellow flash in the middle of the fall petal, which led them into the legitimate route to the nectar, used by the plant's natural pollinators which are bees.

This involved forcing their way into the confines of the tube between the fall petal and the standard petal above, which has the stamen concealed underneath it, so the visitor is forced to pick up pollen on its back.

Once the flower markings had pointed the burnet moth visitor in the right direction it invariably crawled all the way in - and became stuck, unable to reverse out. After a pause and a bit of a struggle the moths finally managed to force their way out through the narrow gap between fall and standard petals - and were always carrying iris pollen when they left.

The interesting aspect of this is that it's an example of a native pollinating insect responding correctly to the floral advertisements of an introduced, non-native flower species that is adapted to bee pollination and that the moths would not have encountered before or co-evolved with. The plants that the moths normally pollinate on the dunes have numerous small flowers with easily-accessible nectar. It's clear that these moths are pollinating the iris and most likely contributing to its seed set.

Yellow Shell Moth

We found this exquisitely marked yellow shell moth Camptogramma bilineata on the sand dunes at Warkworth on the Northumberland coast last week, where it probably breeds on lady's bedstraw.

Click here for more pictures of plants and animals from these dunes.

Stonechats and redpolls

The winter shades of brown still predominated when we followed the path behind Warkworth sand dunes on the Northumberland coast last weekend. The colours of this cock stonechat toned beautifully with the muted background hues.

This is his mate, in more subdued colours.

On the path behind the dunes high tides in the Aln estuary had left a thick layer of last year's decaying vegetation along the strand line, which had become a feeding ground for a flock of about 20 redpolls. Their plumage (apart from their red crown) matched this background exceptionally well.

Seaside beetle

We found this little black snail beetle Silpha atrata, about 1cm. long with beautifully sculptured patterns on its elytra, on Warkworth sand dunes in Northumberland this afternoon.

It's a specialist feeder on snails, with a long narrow head that fits comfortably inside a snail shell opening. Apparently it bites the snail first, with poisonous fangs, causing the snail to withdraw into the shell and secrete bubbles of mucus, which the beetle chews through when it forces its way in to feed on its victim. There's no shortage of Cepaea snails on the dunes for it to feed on. You can see it in action by clicking here and  clicking here

Sounds like the kind of beetle I could do with in my garden, to combat the snail menace.

There aren't many insects about yet, as the promised spring has yet to deliver much warmth, but this is a beetle species that's most often seen in late winter and very early spring. 

Red, Yellow and Blue

There a few spectacles in the British countryside that rival a field of poppies in full bloom. There are two fields at Warkworth on the Northumberland coast that are currently ablazed with these scarlet flowers. Like many plants, poppies produce seeds that can remain dormant in the soil for decades. They require light for germination, so only burst into life after they’ve been brought to the surface by the passing of a plough. Poppies belong to a group of arable weeds that includes corn chamomile, corn cockle, corn flower, corn marigold, bugloss and henbit whose flowering depends on regular soil disturbance, so they have always been a feature of agricultural landscapes since farming first began. In Victorian times all these species were very common, but the development of efficient seed cleaning technologies for cereal crop seed production and the advent of effective modern herbicides have removed them from fields so efficiently that many are now rare. Poppy’s vast seed output has been its salvation. Poppies survive seed burial for long periods and are often revived temporarily when new roads are cut through former agricultural land, or when grassland that was long ago planted with wheat and barley is freshly ploughed.

Behind the dunes at Warkworth, about half way to Alnmouth, there's currently another wonderful floral display in a patch of swampy ground. A single yellow flag iris (above) is a thing of beauty, but half an acre of them in full bloom is something else.......

And a little closer to Warkworth, in a corner of a field that has been left unplanted, there's the most stunning display of bugloss, a cornfield annual that occurs sporadically in the North east but here grows in such abundance that about a quarter of an acre is tinted with forget-me-knot blue.

We lament the fact that some individual wild flower species are becoming rare, but it's even more regrettable that massed floral spectacles like this, once common, are now few and far between...

Poisoners

There’s an interesting collection of poisonous plants growing in the sand dune system at Warkworth in Northumberland. Of these the most notorious must surely be hemlock Conium maculatum (bottom photograph), which produced the poison that the Greek philosopher Socrates used to commit suicide when he was condemned to death for impiety in 399 BC. The dull red blotches on the stems (second photograph) and a mousey smell are key identification features for this lethal plant, whose main toxic compound is the alkaloid coniine, which is also present in several other poisonous members of the carrot family. The middle photographs are of male (lower) and female (upper) plants of white bryony Bryonia dioica, a deadly poisonous member of the cucumber family that was once cultivated as a medicinal herb. In this species the female plants are particularly conspicuous in autumn, thanks to a crop of glossy scarlet berries that look good enough to eat – which would be a fatal mistake. The top photograph shows the poisonous caterpillar of the cinnabar moth Tyria jacobea, which accumulates toxins from the poisonous ragwort Senecio jacobea that it feeds on. Those warning colours ensure that any bird that attempts to eat it and suffers its unpleasant taste will remember the experience and won’t make the same mistake twice.............except that I have a hunch that cuckoos might be immune. We’ve often seen cuckoos feeding on the ground in the dunes at Warkworth when the cinnabar moth caterpillar season is at its height, and I have a strong suspicion that this is the caterpillar that they’re after. If that is the case, then as far as cuckoos are concerned that orange and black colour scheme must serve as a conspicuous advertisement, rather than a deterrent...

Warkworth Sand Dune Flora

The sand dune system at Warkworth hosts a fine flora in early summer. The top picture shows biting stonecrop Sedum acre, whose succulent leaves allow it to thrive on bare sand in drought conditions. Below this is wild thyme Thymus serpyllum, which releases a wonderful herbal fragrance on hot days and hums with bumblebees visiting it flowers. The next flower down is viper’s bugloss Echium vulgare, whose bristly leaves prevent rabbits from grazing it. This too is a magnet for bees and makes an excellent plant for a bee-friendly wildlife garden. It’s a biennial, producing a rosette of leaves in its first year and a flower spike in the second. The seeds persist for a long time in the soil – I introduced some into my garden about 20 years ago and occasional seeds still germinate, without me ever having sown it again. Behind the dunes at Warkworth there’s a remarkable freshwater swamp, filled with the largest population of yellow flag Iris pseudacorus that I’ve ever seen – it must cover the best part of an acre and just now there are hundreds of plants in full bloom.