Aphids!

I have a few plum trees in my garden, which are especially susceptible to very heavy aphid infestations, and this year seems worse than usual.  They don't seem to affect the yield of fruit very much so I am pretty tolerant and make no effort to get rid of them.  If you have a passing interest in insects, one of the benefits of having such trees is that it attracts lots of insects.  Lots and lots of insects!

Many are attracted to the sticky honeydew waste product exudate from the aphids, which is so abundant that it has coated the leaves with a whitish sheen.

Ants, social wasps, parasitic wasps, Blue-bottles, Green-bottles, flesh flies, Sawflies and Hovers (amongst others!) are almost falling over each other to hoover up sugar from the surface of the leaves.

Other insects are attracted to the aphids themselves as a food source rather than the nectar, and home in on the smell of the aphids and the chemical defences that the tree employs in order to protect itself.  Two-spot and Harlequin Ladybirds are wandering across the leaves, leisurely munching through their quarry, and egg-laying as they go.
 

Harlequin Ladybird larva

A couple of weeks ago there were many, possibly hundreds of the migrant hoverflies Episyrphus balteatus and few Scaeva pyrastri buzzing around the tree for a few days, but they disappeared almost overnight, presumably leaving behind eggs.  A quick look at a leaf under the microscope (see below) shows how densely the aphids have colonised the leaves. If you look closely you will also see several yellowy-orange waxy looking larvae which were feeding enthusiastically on aphids.

 

I wonder if these are the larvae of E balteatus at the beginning of their life-cycle?  I'll have to wait to find out because I can't find any early life-cycle pics of the larvae.

The most abundant insects right now are probably social wasps, possibly Vespula vulgaris or Vespula germanica.  These species are predated upon in the nest by one of the largest UK hoverflies, Volucella zonaria, which is expanding its range in the UK.  I took the specimen in the pic below yesterday.  There are not many records from Wales, although I suspect it is likely to be pretty widespread along the warmer and drier coastal corridor. See: http://www.hoverfly.org.uk/portal.php?id=11526&scol=HFF0000&bkgrd=1&ecol=H0000FF&page=4.  V zonaria is a spectacularly large hornet mimic, (about an inch long) and by coincidence one was feeding on the tree yesterday.  I've photo'd it alongside an Eristalsis pertinax, which I'd normally consider one of the larger hovers to give you an idea of the size.

V zonaria and Eristalsis pertinax

Also present (that I managed to get a reasonable photo of!) was the solitary wasp Ectemnius sp.  At least I think that's what it is!

Ectemnius sp

And this parasitic wasp, which looks like a Pimpla sp.  If anyone knows what it is I'd be grateful to hear!

And here's a Scaeva Pyrastri from today (Friday).  The thorax is shiny enough to reflect the background of you look closely!