June 2017

We’ve had yet another unusual spring.  April and the early parts of May have been dry and sunny with no April showers or strong winds.  This has meant that the blossoms have been spectacular and long-lasting.  It seems that everything that can flower has flowered better than ever.  We’ve even had four bluebells come up in our lawn/meadow that we didn’t plant and have never seen since we moved here.  The bluebells in the field at the end of Peter James Lane have been wonderful as well.  One thing that you may not have noticed flowering are the oak trees.  Firstly, oak tree flowers are small, green and inconspicuous, and secondly they don’t flower every year – every 3 to 5 years is typical.  It has been found that oak trees in a forest all flower at the same time.  Beech trees do the same thing.  Apparently, the trees communicate using nerve impulses and chemical signals via their roots and the symbiotic fungi with which they swap nutrients.  The nerve impulses travel at one third of an inch per minute – slow, but maybe not so surprising in an organism that lives many hundreds of years.  This is all set out in a brilliant book called ‘The Hidden Life of Trees’ by Peter Wohlleben, a German forester.  And it’s not mumbo-jumbo pseudo-science either, everything is properly referenced to the appropriate scientific literature. 

There are good evolutionary reasons for this sporadic flowering of the trees (the years that they flower are called ‘mast years’ after the abundance of beech-mast) – firstly, flowering and producing fruit is expensive in energy terms and diverts resources from growing wood and leaves that would be used to harvest more energy from the sun.  Secondly, producing acorns or nuts every year would support a population of deer and pigs that would eat them all leaving none to grow into seedlings.  If all the trees in the forest produce acorns at the same time then there will be too many for the deer population to eat, especially a population that has been thinned by starvation or migration during the non-flowering years.  This is mitigated to some extent by the jays and squirrels that try to eke out the harvest by burying acorns or beech nuts, something that is helpful to the trees, whereas a reduced population of jays and squirrels is not so helpful.  Evolution, though efficient is often imperfect.   

This sporadic flowering of oak trees got me thinking about the knopper gall-wasps (Andricus quercuscalicis), whose bizarre life-cycle I wrote about in November 2014.  To recap briefly, the female gall-wasp lays eggs in the male flowers of the turkey oak; males and females hatch from the oaks, mate, and the females go and lay eggs in the female flowers of the English oak.  The generation that hatches from the English oaks are all parthenogenetic females that reproduce asexually and go on to lay eggs in the male flowers of the turkey oak and so on.  This made me wonder what happens to the gall wasps when there are no oaks in flower. (The gall wasps are not pollinators of oaks, or predators of species that do pollinate oaks because oaks are wind pollinated and don’t produce nectar to attract insects (hence the inconspicuous flowers).   I had assumed that the gall-wasps life-cycle was annual, but maybe that isn’t the case.    So how do the gall-wasps  survive when the oaks don’t flower – do they stay in their galls, if so, how do they know when to emerge?  Or can they survive using the isolated oaks that cannot communicate with their neighbours and flower out of synch?  Do turkey oaks communicate with English oaks?  Is the alternate sexual and parthenogenetic generation life-cycle of the gall-wasp an evolutionary response to the sporadic flowering of the oaks?   Nature is wonderful, but sometimes it just makes your head hurt.

May 2017

Last month I wrote about the small tortoiseshell butterfly which hibernates as an adult.  As spring moves on apace, one of the first butterflies that hibernate as a chrysalis has emerged - the orange-tip butterfly.  The males and females of the orange-tip are different (sexually dimorphic).  The male has the signature orange tips to its wings, whereas the female doesn’t and can easily be mistaken for a small white butterfly.  The female lays her eggs in the flower-heads of lady’s smock (cuckooflower), garlic mustard, or large bittercress amongst several other flower species.  There is a link here in the scientific names – the orange tip is Anthocharis cardamines, lady’s smock is Cardamine pratensis, and large bittercress is Cardamine amara.  It was only when researching this column that I found out that lady’s smock is related to hairy bittercress (Cardamine hirsuta), two very common and very different wild flowers.  The scientific name Cardamine incidentally, comes from its similarity to the cardamom plant, an entirely unrelated species. 

Male Orange-tip

One irritating feature of the orange-tip butterfly is that it rarely settles, at least in our garden, and at rest it is well camouflaged by tucking its forewings into its hindwings which it closes to show the green and white undersides.  This makes photographing them difficult, but last year I managed to photograph a female for the first time, and this year got a photo of the male to complete the set. 

Female Orange-tip

Apparently the caterpillars are well camouflaged as well, so I will be carefully examining our lady’s smock later on to see if I can find any.

Recently while working in the carport, I disturbed a moth.  At first glance it looked like a species I’d not seen before so I dropped my hammer and cable clips and ran for the camera.  Fortunately the moth was still dozy from the hibernation that I’d disturbed, so it was still there when I got back and it posed for several photographs.  Later, comparing the photographs with the moth book, it turned out to be a buttoned snout – a nationally scarce species.  It is called a buttoned snout from the resemblance of markings on its wing to a buttonhole.  It is mainly found in eastern parts of the country and there have been scattered records from along the south coast.  Perhaps the reason for this distribution is the food plant of its caterpillars which feed almost exclusively on hops.  We did have hops growing in the hedge last year so maybe that explains its choice of hibernation site.  This is not a species that turns up in moth traps, so I probably wouldn’t have seen one if I hadn’t been up in the carport sorting out the wiring.

Buttoned Snout - Hypena rostralis

While the spring is racing ahead, it does seem to be an unusually warm and early spring.  Our shed roof was in full flower in mid-April, something that doesn’t normally happen until early May.  (We have a Clematis montana that completely covers the shed roof.)  I also saw workers of both common carder and early bumblebees which shows that their colonies are already in full swing.  I read recently that eleven new species of dragonfly have bred in the UK since 1995, some completely new, some that have previously become extinct in the UK, but all expanding their range northwards from Europe.  All these facts suggest global warming, and all are facts to be ignored by the Trump’s and Cameron’s of this precious world.