Fungus time again

With all the rain we've had this year, I rather suspect we're going to have a good year for fungi: I'm seeing a few on the verges and in my garden, and yesterday I found this season's first specimen of Entomophthora muscae on a hoverfly. In my previous post, I mentioned that the Taphrina fungus alters the growth of the Alder for its own benefit by creating a large surface area for spore production and dispersal. This ability to alter a host for their own benefit is a recurring theme with fungi, and I never cease to be amazed at the lengths they go to in order to achieve this aim.

Entomophthora muscae is a fungus that uses flies as a tool for its spore dispersal. The fungal spores are ingested by the fly and the fungus rapidly grows inside the fly's abdomen. Eventually, the pink fungus breaks through the structure of the abdomen and becomes visible for a couple of days before it breaks down and the spores are released.

This is the shot of the hoverfly from a top-down perspective:

Hoverfly killed by the fungus Entomophthora muscae

The pink fungus can clearly be seen emerging from the abdomen of the hoverfly (which, unusually, is a Platycheirus species: Melanostoma scalare is the most frequent host in this area).

Two aspects of this photograph are of critical importance:

1) the hoverfly is at the very top of the plant (Ribwort Plantain)
2) the wings of the hoverfly are fully extended in an unusual forward-facing configuration

Both of these features will allow maximum airflow over the fungal mass and, more importantly, both are caused by the fungus. Before the fungus kills the fly, it causes it to move to the highest available point and then open its wings to the fullest extent. Then it kills it.

This ability of the fungus to control the fly's movement and configuration for its own benefit is astonishing enough, but it works with different flies from different families, so the fungus has found a way to control the movement of a whole range of different fly species.

Another feature of the configuration control is shown in this side view:

Side view of the fungal mass

The legs have also been fully straightened: yet another part of the configuration that maximises spore dispersal: truly amazing.

The fungal mass will break down and release spores over the next couple of days, leaving just a skeletal husk of the hoverfly on the plant.

It's not only nectaring insects that benefit from the Angelica. This is a shot of the miner Phytomyza angelicastri on the leaves:

Leaf-mining fly Phytomyza angelicastri on Angelica

The Rosy Rustic moth pupates underground until August, and this pristine specimen was resting on a low-level Dock leaf, so I rather suspect it had just emerged.

Rosy Rustic moth

 

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.

Ancient Deciduous Woodland

I have been looking for the Bracken leafminer Chirosia histricina for a few years, now. It's clearly very choosy about where it lays its eggs: A long stretch of Bracken was empty apart from a very shaded section under a Beech. Maybe they like tightly-controlled temperature or humidity.



One of my favourite hoverflies - Leucozona glaucia:



A much more developed case of the fly-killing fungus Entomophthora muscae:

I'm already seeing dead flies on most Angelica plants now. (The fungus is the orange/pink area on the abdomen).


The fungal season has started quite early this year, so I'll show the first images in the next post.

Good old Angelica

At the moment, I'm doing little else other than patrolling the Angelica plants: they'll be gone to seed soon enough.

A welcome return of one of the later hoverflies, Meliscaeva cinctella:

Ichneumonids of various colours and markings continue to nectar: every umbel has a couple.


The first (of many!) of this year's sightings of the effects of the parasitic fungus Entomophthora muscae. The fungus kills the female fly, after having forced her to climb to a high position, open her wings and extend her legs. This maximises the opportunity for spore dispersal once the fungus has erupted through the abdomen.


Traces of the pink fungus can be seen on the back of the abdomen, to the left. The spider's web is incidental, although the fly might well have crawled through it on her last journey.

Fly-killing fungus

For a couple of years, I've been tracking the fly-killing fungus Entomophthora muscae. This fascinating fungus invades the reproductive tracts of female flies - especially hoverflies - and eventually kills them. I can find dozens of dead hoverflies within a few square metres of verge or pathway, so it is clearly an important factor in population regulation.

This is a sample I investigated last year:

http://homepage.eircom.net/~hedgerow21/aug30.htm

From that particular sample I put a few freshly-dead specimens on a slide to see if I could get any spores. Today I remembered to check:



The magnification is x 100, and the spores appear to be rather 3-d and surrounded by a membrane of some kind. I wonder if they're sticky.

Anyway, this fungus is quite fascinating in a number of ways:

It gets ingested by the female fly and migrates to her abdomen. It then begins to expand quite rapidly, emerging from between the tergites as a pink mass. The fungus then compels the fly to climb to the highest part of a stem of grass, or a flowerhead. It then forces the fly to open her wings and extend her legs so that the maximum area of her abdomen is exposed to the wind. It then kills her in situ. The fungus rapidly breaks down and spores are released to be carried by the wind. This compulsion to climb is known as 'Summit Disease', and is an amazing ability for a fungus to have developed.

Current theory (due mostly to genetic sequencing) says that each species of fly is killed by a different form of the fungus. So in future, instead of the generic Entomophthora muscae, we might have e.g. Entomophthora scutellae, and so on.