Friday, 29 August 2014

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.

1 comment:

amanda peters said...

Very intresting post to read...
Amanda xx