Tuesday, March 21, 2017

Slow traveller


I found this solitary wood anemone (Anemone nemorosa) in a shady spot under some ornamental trees at the base of an old dead eucalypt in our garden the other day.  Wood anemones are ancient woodland indicators in South East England, but this was definitely not in ancient woodland.  I reckon the nearest population is about 75 metres away in Churchland Wood.

The plant is known to be able to colonise suitable new sites, but it can, so they say, take hundreds of years.  I suppose though it only takes one successful event for the colonisation to start and this could be one season from year zero or a good deal longer - I don't think the plant is particularly fussy about where it grows: I have seen it in undisturbed grassland as well as woodland.  Once established it will, of course, spread vegetatively as a clone of the original, so perhaps several different clones would make a healthier woodland population, but maybe not.

It has been suggested that new arrivals of this kind may have been transported mechanically as bits of rhizome in some way - on a vehicle, or the sole of a boot.  It is possible that someone walked this one in but the rarity of the plant's arrival in new places means that this is the sort of thing that seldom happens.

The plant is flowering, of course, to attract insects to that central ring of yellow anthers around the green stigmas, and early insects often do visit wood anemones, but successful dispersal of seeds does not appear to be of great value in establishing the plant in new sites (I wonder why)

Wednesday, March 15, 2017

Flowers that "waste their sweetness"

I have always been puzzled by flowers that go to some lengths in terms of colour or scent to appear attractive but, in my experience, are visited by very few insects.  Among those in the garden at the moment are spurge-laurel (Daphne laureola) - see below - which I visit regularly but have found nothing on but a few springtails of the kind that can be beaten out of every tree or shrub.  In mainland Europe they have been shown to be pollinated by pollen beetles (Nitidulidae: Meligethes) but, while several species are not uncommon here, they are either not yet about, or prefer something else. Maybe moths or other insects visit the flowers at night as it fruits well.


Very close to the spurge-laurel we have an ever-extending bed of lesser periwinkle (Vinca minor), Blue flowers are normally rather attractive to insects but, again, these little flowers appear to entice nothing.  Our patch was started many years ago when we first moved to South View and newly weds in the past would often plant periwinkles in their first gardens as it was supposed to promote love.  It seems to have kept Cynthia and I together very successfully.  Its flower is also said to be the item referred to in recommending that wedding gifts should include 'something old, something new, something borrowed, something blue'.


My third 'tries hard' flower is that of the cherry-plum, Prunus cerasifera, also known as the myrobalan.  It is an alien March-flowering species not known anywhere in the wild, but probably from western Asia, and often grown in this country as a hedge or used as a stock for grafting with other fruit trees. Bullfinches are very fond of the buds and these often the reduce the quantity of flower but, clearly, they had not found the branch below though they were going round the garden a week or two ago.

Although I have seen no insect visitors, it is said to be pollinated by bees and, as well as bumble bees, we have at least two species of Andrena on the wing in the garden just now.



Sunday, March 12, 2017

Behaviour of Eudasyphora cyanella, the green cluster fly


Eudasyphora cyanella, a muscid sometimes known as the green cluster fly, emerges from hibernation at this time of year.  I noticed twenty or thirty of them yesterday settling on shiny sunlit leaves of cherry-laurel in our lane.  They did not seem to be interested in other leaves and, if disturbed, quickly returned.

I think the attraction might be that they think the leaves are wet and they might be thirsty.  Some years back I made, in our garden, an artificial tree hole in a bucket filled with water and dead wood over which I hung a sleeve cage so that insects could get in via the lower open end. 



I wrote the below at the time:

On 18th April 2000, a cold, grey day with heavy showers there were, unexpectedly, seventeen of the distinctive muscid greenbottle  Eudasyphora cyanella (Meigen), all female, in the trap.  Several females of this species had occurred during the autumn, but none had been recorded since then.  E. cyanella breeds in fresh cow-dung and larvae have also been recorded from sheep dung .  Both cattle and sheep graze regularly in pastures about 100 metres from the trap, but the insects would have had to fly through woodland and scrub to reach the rot-hole. 

During the next few weeks numbers of E. cyanella rose steadily, though there were several days when none, or few appeared.  Females were quite quickly joined by males and, on the 25th April, there were at least 200 examples in the trap showing a marked clustering behaviour as they gathered on the ‘roof’.  Though they were extremely active, no mating was observed.  During this period several other species of Diptera were, as usual, found in the trap but in nowhere near the quantity of E. cyanella.

On 24th April, a reasonably sunny but quite cool day, I spent some time watching the trap area in the early afternoon.  E. cyanella were sunning themselves on leaves at ground level near the trap and some would rest on the side of the bucket.  On one occasion one was observed on the rim of the bucket apparently drinking from the moisture there and on one of the projecting pieces of wood (these had by now absorbed much water).  On leaving they tended to fly up into the hanging sleeve.  The flies seemed to make little distinction between warm, sunny days and cool, cloudy ones, but numbers were much lower during or after rain, the inference being that there was plenty of free moisture available to drink from vegetation.

By 18th May the numbers of E. cyanella had fallen to virtually nil, but the species was frequently observed in the wider countryside and singletons turned up in the trap until mid-August.

One of the characteristics of Eudasyphora is that, unlike nearly all other Muscids, the adults hibernate in winter.  One of the possible explanations of the observed behaviour was that, after their winter rest, they needed to drink, though why they should be particularly attracted to a rot-hole at a period when plenty of alternative sources of water were available is not clear.  Whatever the reason for their behaviour, it had some further ecological consequences.  They produced, for example, a substantial amount of excrement much of which must have finished up in the rot-hole, thus significantly increasing the nutrient-level of a habitat which is normally nutrient-poor.  At this time the trap also attracted a considerable swarm of the biting midge Culicoides obsoletus (Meigen). They would settle in some numbers on the black netting and in rather smaller quantities on my arms and face.  They bit occasionally, but their main interest seemed to be the trap.  On looking carefully at these midges, they seemed to be more interested in the droppings of the Muscids (which adhered to the netting) than the flies themselves, though I did see them settle on some of the larger species as though to bite.  C. obsoletus breeds in a wide range of moist decaying matter and it has been reported from both rot-holes and sheep dung.  It was not, however, biting in other parts of the neighbourhood and would therefore appear to have been attracted by E. cyanella and the other flies, rather than by myself.

Saturday, March 11, 2017

Mystery topless tables

The other day, while walking in the 'ancient' wood at the end of our garden, I came across two iron structures with no apparent function that I could guess.


I have discovered today that they are temporary protectors to go over coppiced stools where dormice might be hibernating to protect the animals from any accidental damage.  Electricity wires run right through the wood and the power company has to clear the trees back to stop them fouling the wires.  Because it has had dormouse records over a long period to 2016, special precautions have to be taken as it is a legally protected animal and I am told that a licensed dormouse worker oversees the felling and cutting operation throughout.

The work looks pretty drastic, but it should open up the habitat in the traditional way and make it easier for the dormice to flourish.