May 2019 (Stylops, male and female flowers)

I took some photos of solitary bees that were foraging round the garden recently, and I uploaded the photos to a Facebook group to help identify them.  One of them was identified as Andrena scotica commonly known as the chocolate mining bee (from its colour rather than from its diet).  The person identifying it mentioned that it had a Stylops.  I had noticed something attached to the abdomen, but didn't know what it was.  Stylops are a rather gruesome parasitic insect with a bizarre lifestyle.  (Because the lifestyle is so bizarre, Stylops has been used as the logo for the Royal Entomological Society.) They had once been classified as beetles or true flies (Diptera), but are now considered to be in an insect order of their own – the Strepistera, meaning twisted winged.  The larvae hang about on flower heads waiting for a bee to come and pollinate the flower.  They then hitch a ride back to the bee’s nest where they burrow into the bee’s growing larvae.  Once inside the larvae they feed on the insect’s blood and go through several moults until the adult bee emerges, by which time the stylops will be located in the bee’s abdomen.  Male stylops then break out between two of the bees abdominal segments and fly off, but the female stylops stays as a pupa with just her head poking out between two abdominal plates and then emits pheromones to attract a male who fertilizes her using an opening just below her head.  Her larvae will then hatch out and leave through the same opening and drop onto a suitable flower to start the cycle all over again.  The presence of stylops seems not to affect the bee’s ability to fly, or to shorten its lifespan, but it does stop the bee reproducing, which in evolutionary terms means that it loses Darwin’s ‘struggle for life’.

Chocolat Mining Bee - Andrena scotica

Close-up of the stylops - it can just be seen poking out between
2 segments just above the tip of the bee's right wing

I have been reading a lot about Darwin recently.  When he embarked on the Beagle, he considered himself a geologist, though he had been recommended for the voyage by his botany professor who had noticed the talent of the young Darwin.  The botanical work that he pursued after the publication of ‘On the Origin of Species’ is considered at least as important as the work he did on evolution.  It is not surprising that Charles Darwin had abilities in botany as his grandfather, Erasmus Darwin wrote widely on the subject.  (While identifying some of the plant photos that I took in Australia, I came across Darwinia fascicularis – Clustered Scent Myrtle, that was named after Erasmus, rather than Charles).   One of the things that Charles Darwin discovered, was that some plants have separate male and female flowers.  This really surprised me as I thought that people would have known that long before the 1860’s when Darwin found out, especially when people like Linnaeus and Mendel had studied plants so carefully many decades before.

People knew that plants such as primroses had two different types of flower, but nobody had thought to ask why?  Darwin, of course, was doing a lot of asking why, in order to find evidence to support his theory of evolution.  Great experimentalist that he was, Darwin carefully tagged each of one type of flower with ribbons so that he could identify them after they had set seed and the petals had gone.  He found that the tagged ones set seed but none of the others did, thus becoming the first person to identify male and female flowers.  Before this, people had assumed that flowers self-pollinated and that bees visited flowers just for the nectar, they hadn't realized that the flower benefited from the encounter.  For Darwin this supported the essential facet of his theory, the ‘mechanism for change’, without which we wouldn't have all the myriad varieties of flowers that we have now.

Clustered Scent Myrtle - Darwinia fascicularis

April 2019 (Lesser Celandine, nictinasty, Michael Higgins)

In the flowerbed near our front door we have a clump of Lesser Celandine.  It has not been planted there, at least not by us, and is probably the result of a stray seed or a bit of tuber ending up in the soil by some means unknown.  Anyway, it seems happy there and it doesn't clash with any grand garden designs we may have had (we haven’t), so there it can stay.   Lesser celandine (Ficaria verna) is, as the botanical name suggests, considered a harbinger of spring.  It is a member of the buttercup family and is an important forage plant for early emerging bumblebees as well as some early solitary bees and other flies.  It loves shade and in the right conditions will quickly carpet a forest floor with its dark green foliage and bright yellow flowers.  Its leaves and tubers are both edible and mildly toxic, so it is recommended that they are either cooked or dried, which converts the toxins to something more benign, before making a feast of them.  The knobbly tubers also give the plant its other common name – pilewort.

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As a buttercup, they come within the family Ranunculaceae, which comes from the Latin ranunculus for ‘little frog’.  Though I have searched the Internet for a better explanation, the concensus seems to be that it is called little frog because buttercups live near water like frogs do.  There must be a better explanation than that, mustn’t there?

Lesser Celandine closed

Talking of explanations, you may have noticed another feature of lesser celandine – the flowers close by mid-afternoon and don’t open again until the following morning.  There are several plant species that do this, one of the most striking is goat’s-beard, which has the alternative name – ‘Jack go to bed at noon’ because it is never open in the afternoon.  Apparently there are some specialist cells at the base of the petals in a structure call the pulvinis.  The chemistry of these cells changes so that they swell or contract to move the petals open or closed.  It is thought that this is a response to temperature changes and possibly daylight as well because on cold dull days the petals don’t open at all.  The big question, of course, is why does the flower need to close anyway?  Why not display itself to passing pollinators all the time?  Perhaps the plant doesn’t want to attract pollinators when there is not enough energy from the sun to produce nectar, or maybe it is to avoid damage from sudden frosts.  The fact is that nobody yet seems to know.  Incidentally, the word that describes this process for both petals and leaves is ‘nictinasty’!

The faintly variegated leaf of Lesser Celandine

If you have followed this column for any length of time you will know that I’m always banging on about threats to our wildlife, loss of habitat, pesticides, insect declines, etc.   But it seems that I’m not alone.  I found this quote from a speech at a conference on biodiversity given by Ireland’s president Michael Higgins recently and just had to share it with you.

“Around the world, the library of life that has evolved over billions of years – our biodiversity – is being destroyed, poisoned, polluted, invaded, fragmented, plundered, drained and burned at a rate not seen in human history - If we were coal miners we’d be up to our waists in dead canaries.”