Pollinators

This week I was giving a talk as part of an international conference about pollinators. If you mention pollinators most people immediately think of bees, and bees are certainly extremely important plant pollinators. Other groups of insects, however, are also important in the pollination process, and I was covering hoverflies. I spoke to the other speakers on non-bee pollination (one discussing beetles, another covering butterflies and moths and a third talking about ants), and it was clear that there is actually very little scientific literature out there that discusses and compares the contributions made by these other groups.

I made the case that since there are more species of hoverfly than bee in Ireland, and there are clearly more hoverfly specimens than bee specimens, that hoverflies are obviously an important player in plant reproduction. Yes, bees are 'busier', visiting more plants per minute than a hoverfly, but bees also take pollen back to their nests to feed their young. This takes pollen OUT of the plant reproduction process, rather than assisting. Further, there are bees that short-circuit the nectar-taking process by cutting into the rear of flowers, thereby bypassing the pollen-gathering part of the arrangement. This is theft.

I then went on to discuss the lifecycle of hoverflies, and pointed out that some species of hoverfly lay their eggs in bee nests. Their larvae eat the detritus in the nests, keeping them healthier and more productive. So hoverflies are assisting some bees. Lastly, I discussed the fact that some hoverfly larvae feed exclusively on aphids: yet another beneficial aspect to this group.

The beetle and ant speakers struggled to find any evidence of plant pollination other than incidental or accidental transfers as they moved from plant to plant. The one saving grace as far as ants are concerned is that they 'farm' aphids, thereby providing a food source for the hoverfly larvae!

After the talk we went on a tour around the excellent conference site (Oxford Island at Lough Neagh) and I took the camera with me.

The following shots show how things are progressing with the new 70D camera.

This is the original shot (reduced in size!) of the hoverfly Eristalis pertinax:

Eristalis pertinax - original full-frame shot

This is the same image cropped to show the whole insect:

Original image cropped to the insect 

And this is a crop to just the wing veins:

Crop showing just the wing veins

These three images were all taken from the same original. This camera continues to astound me with its performance.

The image is also instructive in another way: In the field I initially identified this as Eristalis pertinax. But when I blew it up on the computer I noticed the dark wing shade and the yellow margins to the abdominal tergites. The only species on my patch that looks like that is Eristalis horticola, so I changed my identification without any further thought.

I showed the images around and was informed that this was indeed Eristalis pertinax, and that occasionally it can have a dark wing shade! Lesson learned: although I can safely identify my local set of species, I need to take into account variations that might occur outside my immediate geographical area.

Someone found this mine on Wood Avens and brought it for me to look at:

Mine of Stigmella aurella on Geum

I immediately recognised this as a Stigmella mine (central frass in a corridor mine), but didn't know which species of Stigmella mines Geum. So I took the images and went back to the office to check the internet. Turns out it's the very common Stigmella aurella, which I have often shown on Bramble. Bramble and Geum are both members of the Rosaceae, so they're quite closely related. It's nice to get confirmation from details like this that the plant taxonomists were right!

Finally, I found a few pristine specimens of the Parasol Mushroom, Lepiota procera:

Lepiota procera - Parasol Mushroom

I think I'll have a fungal foray to Ards on Sunday.

Gap in the rain

Normal service has been resumed after wonderful weather in March, and I have been sitting (no, standing!) glowering at the rain for the last few days. I spotted a short burst of sun, so I rushed off to the most likely spot for a few moments.

The patches of Celandines are all fully open in the middle of the day, so the insects were making the use of the gap in the weather, too. The following shots of hoverflies illustrate some of the difficulties we have in making accurate identifications.

This is a male (eyes meet in the middle) Melanostoma species:

Male Melanostoma mellinum on Celandine

The (relatively) short abdomen leads me to Melanostoma mellinum, because the alternative, which is Melanostoma scalare, has a much longer abdomen in the male.

Notice the very slender front feet.

Next we have a male Platychierus sp. (notice that the front feet are much wider and longer than those of the Melanostoma). The legs also appear to be more robust than those of the Melanostoma.

Male Platychierus sp.

If I was a gambler, I'd say Platychierus albimanus, but I'd like a look at the abdominal stripes before committing.

The next is quite a different beast altogether. It's a female (eyes don't meet in the middle) Cheilosia sp. Cheilosias are darker, chunkier and larger than the two previous families, and although it's difficult to detect from this shot, the wings have a bronze tint to them. Other shots leave me quite convinced that it's Cheilosia albitarsis, and the size is ok for that, too. 

Female Cheilosia sp.

This male Eristalis pertinax was basking on a Buttercup leaf:

Male Eristalis pertinax

Given the absolutely pristine condition (clean feet, shiny wings, clean hair, no pollen), and the fact that the wings look a very little on the small side, I'd say this had just emerged and the wings still have to finish inflating.

And this is also an emerging specimen: the first Common Carder Bumblebee - Bombus pascuorum - of the year. This has to be a queen, although these are much smaller than the queens of the darker bumblebees that we have around here.

Emerging Bombus pascuorum queen

This 7-spot Ladybird was running around leaves and flowerheads looking for aphids. Given the speed of the chase, this was a very difficult shot. No time for basking in this case:

7-spot Ladybird

It's really full speed ahead on all fronts at the moment. This Common Dog Violet - Viola canina - is also just opening: the petals still have to rotate to their final positions.

Viola canina

I've included a side shot to show the pale, notched, spur that identifies this species:

Hartstongue fern is usually the first to unravel. I have 15 or 16 different species of ferns on this stretch, so we should be able to follow the sequence of these as they open up:

Not bad for about 10 -15 minutes.

Playing catch up

In the normal order of things, higher order species tend to prey on lower-order species, so wasps and bees tend to be predators on flies (or members of their own order). The Conopid fly Sicus ferrugineus, however, reverses this trend. These are parasitic on bumblebees, stapling a single egg into the soft underside of the worker's abdomen. This oviposition is said to take place in flight, but I have never seen it happening. Once the bumblebee has been parasitised it tends to change its feeding habits, presumably to the benefit of the fly larva.


Mesembrina meridiana is easily recognisable due to the orange wing base. The name indicates that it is a noon flyer, and that's when I usually see them.


Angelica has flowered and that means plenty of shots of nectaring insects. this is the Tree Wasp - Dolichovespula sylvestris. It has an overall orange feel to the colouration and the antennae bases are yellow. Facial decoration is a single small spot.


This male hoverfly looked unusual, but it consistently keys out to the very common Eristalis pertinax.


Trombidium sp. mites are usually seen scrambling over the base of plants as they search for rotting vegetation. This one was sunning on a grass blade.


Those of you who have been following my websites for a few years will know that this is one of my favourite flowers: Slender St. John's Wort - Hypericum pulchrum. The latin name shows that I'm not alone in that opinion.


This pristine flower of Meadow Buttercup - Ranunculus acris - caught my attention:


Finally for today - Eyebright. That's as far as the id is going.

Drumboe insects

Drumboe has a very rich insect population: I find some of my most interesting species here. This is Nomada leucophthalma, which is parasitic on the mining bee Andrena clarkiella. This is yet another prime example of dependency timing: A. clarkiella uses only the pollen of willows to feed its young, and willow pollen is only available for perhaps 6 weeks of the year. So the Nomada must locate an available Andrena nest and lay its own eggs there in a very short timeframe. Nomada sp. are known as kleptoparasites: they use the pollen the Andrenas have collected for their own offspring.


This specimen was flying along the vertical earth bank looking for Andrena nests. They fly facing the bank and move sideways as they search. This behaviour can be seen for only 4 weeks of the year. Shot was manual focus!



This is an Andrena, but not the one parasitised by the above Nomada. Andrena haemorrhoa, about 15 mm long:



Smaller hoverflies are making an appearance at last. This is a male Melanostoma scalare:


The larger Eristalis pertinax has been around for a couple of weeks. This is a female:



A single Speckled Wood was the first of the year for me. I also saw one Orange tip male and a Green-veined White, both of which I showed the other day.


St. Marks Flies are so-called because they usually start to appear around St. Marks day - April 25th. They're usually pretty accurate.


I have never found a convincing identification for this one, but it should be Bibio marci.

Drumboe

Drumboe Wood is that strangest of creatures: an ancient urban woodland. It lies no further than 100m from the main shopping centre, separated from the main road only by the river Finn. Its great age leads to a huge biodiversity, with some very rare species. Indeed, it is the only known location in Ireland for Cerodontha sylvatica, which I added to the Irish list in 2006.

The Bluebells seem to be quite early this year:


These are the first flowers of Cuckoo Flower - Cardamine pratensis. My local specimens haven't flowered yet, so I suspect Orange Tip butterflies are still about 2-3 weeks away.


This moss is Rhytidiadelphus triquetrus. It's supposed to prefer calcareous soil, but I find it in acidic woodlands and in heath. One common name is 'electrified cat's tail moss'. I can see why.


My first hoverfly of the year: Eristalis pertinax. this one was smaller than most, and I had to eliminate E. nemorum and E. arbustorum based on the pale legs.