What's the model for this mimic?

Hoverflies, without stings, are well known for mimicking the colours and patterns of stinging wasps so the standard issue markings for most hoverflies are some variation on the theme of black and yellow stripes. This species, Leucozona glauca, is the exception to the rule and is turned out in this attractive black and denim blue colour scheme ...... which begs the question as to whether it's mimicking something or is simply a genetic variant with no particular natural selective benefit or disadvantage. 

According to British Hoverflies by Alan Stubbs and Steven Falk the markings on this species are normally yellow but this blue variant occurs frequently.  I haven't encountered it often and this one is part of a population that lives along a woodland ride in Hamsterley Forest, Co. Durham and is often quite abundant when hogweed and angelica are in flower. This individual is a female, identifiable by the widely spaced eyes.

It seems to have been quite a good summer for some hoverflies in my part of Co. Durham. I had a quite a few of this one, which I think is a particularly attractive variant of Helophilus pendulus, in my garden where it seemed to be partial to meadow crane'sbill flowers. 

I'm not completely sure what this large hoverfly species is but I think it may well be Sericomyia  silentis..... a convincing wasp mimic. It's been quite common in Teesdale throughout August and early September and I've seem several on  devil's bit scabious, which is supposed to be particular attractive to this species.

Gaudy Froghopper

Several bloggers have recently posted images of this gaudy little froghopper Cercopis vulnerata, which reminded me that it's a long time since I've seen one - until today. This was one of several amongst the leaves of rose-bay willow herb.

Unlike the familiar brown froghoppers whose larvae develop in a frothy mass of 'cuckoo spit' on plant stems, this species' larvae develop underground on plant roots, where several huddle together in a patch of solidified froth - perhaps on the roots of the rose-bay willow herb plants.

A Tale of Two Tails

A red-tailed bumblebee Bombus lapidarius busy collecting nectar from the chive flowers ....

.... and a little further down the flower border, collecting nectar from a scabious flower - Volucella bombylans, the hoverfly that mimics the bee's colour scheme.

There are two common forms of V. bombylans - this one and another with yellow fur on the body and a whitish tip to the abdomen that mimics the white-tailed bumblebee. The hoverfly larvae feed inside wasps' nests - how they avoid being eaten by wasps is not known. Most years we have a wasp nest in the garden somewhere, so this hoverfly is usually around.

There's more mimicry here

Menace

I found this unusually colourful female cranefly Nephrotoma crocata busy laying eggs in the flower borders in Durham University Botanic Garden. This wasp-like colour scheme looks like a fine example of mimicry,  pretending to be something dangerous as a means of defence, and its jerky movements as it poked its tail end in the soil added to a convincing air of menace. It's harmless though - a 'sheep in wolf's clothing'.