Monday, 23 May 2011

Still raining

The weather has continued to be very wet, with rain every day of May and an associated slowing-down of sightings. I have managed to sneak out in the less wet spells, however, and made the best of the bad light.

Lady's Mantle tends to sneak up and surprise you. One day it's invisible, and the next the flowers are out. The large folded leaves are ideal for insects such as micromoths to make their larval 'spinnings' for their shelter.

Lady's Mantle

The fronds of Male Fern have only just unfurled and the spore-bearing sori are already in place (although they will remain empty for quite some time, yet).)
Sori of Male Fern
The hedgerow has at least five species of Potentilla (and also the hybrid P. x mixta) in various places along its length. Silverweed is one of the easiest to identify, with its downy silver leaves:

The striking Marsh Cinquefoil is currently in bud, so I'll show pictures of that very soon, weather permitting.

The Orange Tip larva that I showed the other day is now about 4mm long. Note the damage to the seedpod, which the larva has caused by eating it. This is the only foodstuff that the larva will ever eat, moving from one pod to another as it finishes each one off.
Orange Tip larva showing pod damage

Bumblebee workers are busy in the gaps in the rain. They're still very small, so I suspect the rain has limited their pollen-gathering ability to quite an extent.

Bumblebee worker landing on Raspberry flower

Ichneumonids have started to appear in large numbers, which is no great surprise: their target moth and butterfly larvae are fattening up nicely, now.

Ichneumonid on Cow Parsley

Ichneumonid (left) and the hoverfly Syritta pipiens
The second shot also includes a rear view of a male Syritta pipiens hoverfly.

The next shot took me a couple of hours to tie down to species. It's a Lesser Dungfly which keys out to Cordilura rufimana. The Cordilura family is quite large, with some 22 species on the BI list. Most are dung-feeders as larvae, but C. rufimana appears to feed on the rootstock of various plants.
The Lesser Dungfly Cordilura rufimana
Surprisingly similar, but totally unrelated, is the Stilt Fly Neria cibaria. These have a strange habit of lowering their mouth to the upper surface of leaves and then rocking backwards and forwards on those long legs, shaving the upper surface of the leaf, presumably for food.

Neria cibaria - a Stilt Fly
A couple of sawflies next:

The first is on Broad Buckler fern:
Sawfly on Broad Buckler fern
And this is one of the Tenthredo sp.:
Tenthredo sp. Sawfly 

The Hoverfly Cheilosia albitarsis is an associate of Creeping Buttercup. The extremely similar (and only very recently segregated) Cheilosia ranunculi is thought to associate with Bulbous Buttercup.
The hoverfly Cheilosia albitarsis

Two shots of very small (6mm) soldier beetles from the Rhagonycha family: 

First, Rhagonycha limbata: 
Rhagonycha limbata
And secondly, Rhagonycha lignosa, which is associated with Hawthorn flowers during the early part of its season, and can be separated from the species above by the all-dark thorax:
Rhagonycha lignosa
Rhagonycha lignosa is a new species for my list.

A couple of weeks ago, I showed one of the pollen-stealing cuckoo bees. This one looks to be another member of the same family: Nomada flava.

The kleptoparasitic cuckoo bee Nomada flava

Rhagonycha section of this page has been updated to correct the identification of Rhagonycha lignosa.

Saturday, 14 May 2011

Double delay

After a wonderful April, it has rained every day in May so far, sometimes very heavily. Blogger has also been offline for a few days, so I have a bit of catching up to do.

Worker Bumblebees are very numerous now, although most of the current ones are from the queen's first batch of eggs and are therefore very small. The ones gathering pollen from Raspberry flowers are scarcely larger than a pea:

Worker Bombus lucorum agg.
Hawthorns are in full flower now, and in keeping with the trend this year are bearing many more flowers than usual. Some trees are almost entirely white (and some are almost entirely pink!). The fresh flowers have pink interiors, but that very quickly disappears, leaving a much duller flower:

Hawthorn blossom - "May"
Hawthorn blossom is known as 'May', and is the origin of the northern saying: "Ne'er cast a clout e'er the May is out". Which translates to "Don't divest yourself of warming clothing until the Hawthorn has flowered".

The hoverfly Cheilosia grossa feeds on Thistles as a larva. The larvae can be detected by their effect on the host plant: any thistle that branches from ground level and appears dwarfed can be considered to be potentially 'occupied':

Male Cheilosia grossa

I already showed the first of the Orange Tip butterfly eggs here. The female lays a single egg behind the flower, waiting for the seedpod to develop. She lays only one egg because the larvae are cannibals: any young larva will be consumed by an older one. In the early season, I only ever find a single egg per plant: females detect the presence of an existing egg and will move on to other suitable plants to lay their eggs. At the end of the season, however, all the suitable plants already have eggs and I find what I call the "Let's dump eggs on all the plants in case one might just actually make it" syndrome. This photo shows at least 14 eggs on one plant:

Orange Tip eggs and larva
And top of the class to anyone who spotted the first Orange Tip larva on the seedpod at the front of the picture.

The important thing to realise here is that synchronisation is crucial: if you emerge before the host plant is ready, you will have nowhere to lay your eggs. If you emerge too late, then all the suitable (southwest to south-facing plants on an embankment to catch the sun) plants will already be occupied and your late larvae will have to hope that they don't encounter one of the early occupiers. The window of opportunity is perhaps 14 days. This theme of critical synchronisation occurs time and time again in our wildlife.

The next shot illustrates one of the most stunning aspects of our natural history:

Female Dungfly infected with Entomophthora muscae fungus
The image shows a female Dungfly that has been killed by a fungal infection. The fungus Entomophthora muscae enters the digestive tract and progresses to the abdomen where it multiplies and expands. As it expands, the pink mass begins to break through the abdominal segments as shown above. But now we come to the crucial bit of the exercise: before the fungus kills the fly, it compels the fly to climb towards a high point and then to open her wings. Then it kills her. This combination of high position and open wings affords the maximum opportunity for wind-borne spore distribution for the fungus. So the fungus gains control of the movement of the fly in order to maximise the opportunity for dispersal of its spores.

Wednesday, 4 May 2011

Four wings good?

I usually associate the first damselflies of the year with fern fronds, because they use them as perches to sun themselves and as launching pads for a leap to catch their prey. This year, however, the ferns are still unfurling and the damsels are having to resort to Bramble for resting on. This is a female Large Red Damselfly:

Female Large Red Damselfly

The standard definition of Diptera, or flies, is that they have only two wings. This is true, but only to a certain extent. Flies do indeed have only two wings in the conventional sense, but they also have two modified wings: the halteres. This shot shows the two halteres - located just behind the large, main wings - of a Cranefly:

Halteres of Cranefly
The halteres vibrate at roughly 45 degrees from the axis of the fly, but at 90 degrees to each other. Due to the coriolis effect, they act as gyroscopes and transmit information about rotation to help the fly to stabilise during manoeuvres. Bees, wasps, butterflies, moths, dragonflies and many other insects have 4 wings, but flies generally have more manoeuvering and hovering capability due to their combination of two wings with two halteres.

When I'm looking for moths at night, I often find other insects attracted to the light. This Cockchafer was hanging on my wall last night:

Cockchafer beetle
The Cockchafer has a very interesting lifecycle: the larvae live underground for three or four years, and the adults tend to be seen more frequently in three or four year cycles. There appears to be another cycle of perhaps 30 years, when the beetles are seen in huge numbers. The specimen in the picture above appears to have lost its right antenna.

The micromoth in the next shot has a glorious name: Schreckensteinia festaliella

This moth always lands with its middle legs outstretched and pointing upwards. I suppose with all those spikes, it must be the only safe place to put them.

As I have mentioned before (and will doubtless mention again), Pug moths are rather difficult to identify to species. The Foxglove Pug can be separated from the very similar Toadflax Pug by the 'notch' in the outer edge of the dark bar, as indicated by the arrow: 
Foxglove Pug, showing notch in wing bar
Size and timings are also different between the two species, but without a comparison, and given the very early season we're having, we have to act on the clues we are left with.

Monday, 2 May 2011

All new moths

The good weather has encouraged a number of moths to emerge in the past few days, many of them much earlier than we would usually expect to see them. Moths are generally tied to specific plants or plant families, so the basic rule is: the more native plant species you have in your area, then the wider will be the variety of species of moth you will be able to find.

My first new moth for today comes with a little bit of controversy: many moths are bivoltine - they have two generations per year. This is complicated by the fact that some species have two generations in southern areas, but only one generation in northern areas. The Engrailed moth has tentatively been divided into two species - Engrailed and Small Engrailed, largely based around the number of generations in different areas. The picture is currently far from clear, and perhaps we're just part way through the evolution of a new species. Until the matter is resolved, we have to refer to these specimens as Engrailed/Small Engrailed.

Engrailed/ Small Engrailed

Both species feed on a wide range of trees and shrubs.

The Dark-barred Twin-spot Carpet can be separated from confusion species by the 'notch' in the front edge of the dark band on the wing. The larvae feed on herbaceous plants such as Dock. 
Dark-barred Twin-spot Carpet

Nut-tree Tussock feeds on broad-leaved trees as a larva:
Nut-tree Tussock
Everyone knows that Swallows fly from Africa to nest here every year. It's fairly well-known that butterflies such as the Painted Lady and Red Admiral can make a similar journey. What is much less well known is that we have micromoths that are also migrant. The Diamondback moth is only about 10mm long, but if the wind is right, then we can find them in good numbers in favourable years. They are too delicate to survive our cold winters, so we can be sure that any we find have made the journey from the Mediterranean area:

Diamondback moth 
I'm waiting for confirmation of the identity of this moth that came to light last night, but I'm fairly confident that it's Glaucus Shears:
Glaucus Shears - tentative identification

This moth is a good example of the effect of habitat: they are only found very near their host plants; Heathers, Bilberry and other heath plants. Also suspected to be migrant.

All of these moths are new to me, so my Species Index has suddenly leapt to 1393 species.