Wednesday, December 13, 2017

On ivy berries

The berries on our native ivy seem to be ripe already.

This is quite early for them, often they will not be ripe until well into spring.  There are many birds that eat the berries though the seeds pass through their gut (seed dispersers).  Woodpigeons are also very fond of them but they digest the seeds (seed predators).  The fruits are nutritious with a high fat content but they are toxic, though birds normally seem to be able to deal with the toxins.  Barbara and David Snow in their splendid book Birds and Berries (T & A D Poyser, Calton, Staffordshire. 1988) say that woodpigeons destroy most of the ivy berry crop.

We also have a bush of arborescent Persian ivy (Hedera colchica) but the seeds on this are still unripe.  It makes a non-climbing dome-shaped bush about two metres high that is convenient for watching the various insects that gather on the blossoms in the autumn.

One conundrum regarding ivy berries concerns the holly blue butterfly (Celastrina argiolus).  Many books say that the larvae feed on these berries among those of other plants.  Jeremy Thomas, for example, says in his Butterflies of  Britain and Ireland (1991) that "larger ivy berries may also be completely devoured, but the cups remain as evidence."  He also says the eggs of the summer generation are laid on ivy buds.  The larvae occur in May and June and August and September so they are not normally present when there is any appreciable crop of ivy berries and I wonder if the flower buds are sometimes confused with fruit.  Whether buds or berries, holly blue larvae eat the insides rather than the outsides and the 'cups' to which Jeremy Thomas refers must be the outer layer of the buds (or fruit) as they do not have cups like acorns.

Richard South in his classic 1915 The Butterflies of the British Isles quotes extensively from a paper by Adkin describing how the second brood larvae tackle ivy buds, saying in conclusion that they quit the buds in order to pupate.

Tuesday, December 12, 2017

Cold snap December 2017

It has been very cold over most of the country.  Last night the temperature fell in our garden to -2.6 C but in Shropshire -13 C was recorded.  The thin layer of snow that remained from yesterday froze hard and produced a lovely crunchy surface on the dead leaves in Churchland Wood.  It was like walking over crisps.

Monday, December 11, 2017

Blackbird, munchkin and snow

Our granddaughter has recently cleared the area outside our kitchen window between the path to the backdoor and the hedge as part of our intermittent attempts to manage it as a mini nature reserve.  A couple of days ago we put a small slightly rotten orange pumpkin (sold as a munchkin) in the centre of the area.  I bought in October as a small gesture towards Halloween and wanted to watch what would happen to it as it decomposed.  Yesterday the female blackbird at the top of the picture put in an appearance and was flicking leaves over in search of food.  Among other things she found fallen berries from the nearby rock whitebeam tree (Sorbus rupicola).  Her activities started to bury the munchkin (which she did not touch) with a layer of leaves and I reflected that birds must often help objects laying on the surface slowly to get covered up and buried.

Today we had our first snow of the winter accompanied by much hysteria on TV.  We caught a snow belt that moved in from northern France (closing the port of Calais) but we were right on the edge and it all melted quite quickly.  However, I think it is one of the coldest spell we have had in December for a long time.  The photo is a wider shot of the munchkin area much patronised by Mrs. Blackbird and, today, her mate.

Friday, December 08, 2017

On wingless females

Yesterday evening a male winter moth (Operophtera brumata) was attracted to the light from our kitchen window pane.

I know it is a male because the females are micropterous - almost wingless - and unable to fly.  In the past when I arrived home by car in winter I would often see dozens of males fluttering in the headlights along woodland lanes, but they do not seem to have been so common recently.

As a small boy, friends and I used to look for females of this species and mottled umber moths on the bases of tree trunks and in Canada I once saw several males similar to the winter moth fluttering round the base of a tree trunk where there were wingless females.

I used to wonder why some insects had this wingless female dimension.  Other examples are the vapourer moth and the autumn flying cranefly Tipula pagana.  The best explanation I have come across is by Malcolm Scoble in his book The Lepidoptera and I think it worth quoting at length:
Wing reduction is strongly related to environmental conditions.  Those few species where males are affected inhabit coastal habitats or small oceanic islands, areas where wind conditions are such as to prevent individuals flying directionally towards potential mates.  Jumping is a typical mode of progression in members of these species.  Wing reduction in females is strongly related to the degree of egg maturation at eclosion.  Well developed eggs leave little room for the flight muscles, which become reduced.  Reduction of flight muscles leads to flightlessness, a first stage in wing reduction,  Tympanal organs, which occur mainly at the base of the thorax or of the abdomen, also tend to become reduced or lost.  Females emerging from the pupa with well developed eggs have no need to sustain themselves while the eggs mature.  As long as males can find them, and provided eclosion occurs on a suitable foodplant, these females can lay their eggs rapidly.  Species exhibiting these characteristics are often active in the cold season (e.g. many Geometridae) where rapid oviposition, occurring before extreme conditions overtake individuals, is clearly advantageous.
In other words you can mate and lay all your eggs before you and your partner freeze to death and, since it is winter, you may be less likely to be eaten by a bird.
Reference: Scoble, Malcolm J. (1992)  The Lepidoptera.  Natural History Museum Publications, Oxford University Press

Wednesday, December 06, 2017

Late flying moth

A yellow-line quaker moth (Agrochola macilenta) settled on the outside of our kitchen window yesterday night.  It is an autumn-flying species, but rather infrequently recorded as late as December.  It is said to be attracted to decaying apples.  A. macilenta is a widespread species in England with larvae that feed on a variety of deciduous trees or, in the north, heather (Calluna).

The adult moth is rather sparingly and inconspicuously patterned (macilenta means 'lean' or 'meagre' referring to the markings), they are however distinctive especially the yellow and red almost straight submarginal lines that do not quite make it in good order to the wing tip.

Monday, December 04, 2017

Winter bumbles

On milder days the flowers on the Oregon grapes in the garden are attractive to late flying bumble bees.  The example above is, as far as I can tell, a buff-tailed bumble bee (Bombus terrestris) worker.  One feature of this is that it has a very narrow band of buff hairs between the black and white bands at the end of the abdomen.  The species is also known to have a third, winter-flying generation whose workers visit oregon grape and other winter flowering shrubs.

This Oregon grape is Mahonia x media 'Charity' which originated in a nursery in Northern Ireland and was selected in a Surrey nursery.  We have several different Mahonia species and hybrids in the garden but 'Charity' is among the most attractive.  The fruit of Oregon grapes can be used to make jams, jellies and in other recipes.  It has both an Award of Merit and a First Class Certificate from the Royal Horticultural Society, so it ticks nearly all the boxes: ornamental evergreen foliage and fragrant flowers in winter; edible fruit; attractive to wildlife.

Saturday, December 02, 2017

On the different lords-and-ladies

One of the most striking plants in late autumn and winter is Italian lords-and-ladies (Arum italicum) whose leaves appear in October or November whereas the commoner lords-and-ladies or cuckoopint (Arum maculatum) do not appear from the ground until late winter, January of February.

In our garden we have two subspecies of A. italicum: subsp. italicum and subsp. neglectum.  The latter plant is a native from West Sussex westwards, usually close to the coast, while the nominate subspecies is a garden plant that has escaped into the wild quite widely.  It has very distinctive leaves marked with white along the veins (sometimes described with the longer name Arum italicum subsp. italicum 'Marmoratum') whereas the veins in subsp. neglectum are far less of obvious.

The native species does not grow wild in our area so far as I know but A. italicum italicum occurs in a number of woods and hedges locally (some may be hybrids between the two subspecies).  Some of these are a long way from the nearest gardens and may be bird sown.  The plant depicted below appeared of its own accord on the shady side of a hedge in our garden and is steadily increasing in extent.

The second picture is of native subsp. neglectum and the third of common lords-and-ladies photographed in February in an earlier year.  The italicum were photographed earlier today and the leaves have been up for some weeks.

Refreshing my data on lords-and-ladies sent me to the bookshelf for Cecil Prime's wonderful monograph, largely on the British Arum species.  It covers not only the biology, ecology and distribution of the plants but includes fascinating information on its economic uses, folklore and vernacular etymology.  A masterly study -do get a copy: Prime, C. T.  (1960 and 1981)  Lords and Ladies. Collins New Naturalist series.