"A Nature Observer′s Scrapbook"
Hoverflies
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Marmalade fly
Episyrphus balteatus
Sometimes known as the Marmalade Fly, this is a very common hoverfly throughout Europe and is considered to be a possible migrant as it is found in large numbers in coastal areas.
Very much a friend to the gardener, in a larva's 14 day development period it is credited with consuming several hundred aphids. A newly hatched maggot-like larva, blind, white and almost transparent, is quite capable of of tackling an aphid much larger than itself.
The adult fly satisfies itself with nectar as it busies itself with pollination. Favoured wild plants appear to be Cow Parsley and Hogweed - although the pictured dandelion flower attracted a lot of attention, too.
Some very good high definition images are to be found by doing a search at www.bioimages.org.uk
| Date | Sighting |
| 02.06.2003 | On Cow Parsley by roadside ditch. |
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Sun-fly
Helophilus pendulus
Earns its common name because it is reputed not to appear until the sun is shining brightly.
There are several Helophilus species (described in some detail at this Dutch link), all exhibiting the distinctive longitudinal stripes on the thorax.
H. pendulus is said to be 'common' but is not a regular visitor to my garden. All Helophilus species favour ponds and muddy water. Perhaps my pond is too clean for them but there is a muddy ditch running down the side of the garden. Or, maybe the sun just does not shine brightly enough on me!
The male in the upper image was rubbing its front feet together prior to grooming and gives the impression that it might have only four legs and two pairs of antennae! The female in the middle image has slightly different markings and appears broader across the abdomen. And the side view of the female is included because the leg markings are a significant species identification feature.
The aquatic larvae, like those of the Eristalis hoverflies, are 'rat-tailed' maggots, and are to be found in stagnant water from May to November.
| Date | Sighting |
| 23.08.2005 | Nectar sipping from Purple Loosestrife (Lythrum salicaria) in bright sunshine. |
| 01.10.2005 | Female found sheltering from a blustery wind on the lea side of an Elder tree. |
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Hoverfly -
Syrphus ribesii
A common UK hoverfly flying from April through to November.
And, in its larval state, is an aphid eater extraordinaire, consuming hundreds in its two week larval state.
| Date | Sighting |
| 15.08.2004 | On Sedum spectabile in back garden. |
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Hoverfly -
Eupeodes luniger
At first sight, easily confused with the previous species (and others! I originally thought this to be Scaeva pyrastri until I was corrected.).
E. luniger has gently hook shaped yellow markings with a very distinct gap down the centre of the abdomen. The markings also fail to reach the outside edge of the abdomen.
This species is to be found from Nth America, through Europe, Western Asia and Nth Africa.
| Date | Sighting |
| 31.07.2004 | On Salix caprea pendula in back garden. |
| 18.09.2005 | Resting on Dogwood in back garden. |
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Hoverfly -
Eristalis pertinax
There are two very similar species of Eristalis, E. pertinax and E. tenax. The species shown on the right is the former, recognised by the bi-coloured tibias of its hind legs. The hind legs of E. tenax are uniformly dark.
The thin white bands between the abdominal segments, seen in the upper image, are not a regular feature and are caused by flexing of the body.
The same species in the lower image is seen in a more normal, relaxed position.
The female will lay her eggs in damp manure heaps or close to stagnant water. In water, the grey larvae swim freely and can extend a breathing tube a staggering 100mm or more to the water surface, earning them the name of 'rat-tailed maggots'.
A good reference is to be found at
http://www-biol.paisley.ac.uk
Although E. tenax, commonly known as the Drone Fly, is reputed to be commonly distributed throughout the UK, I find that I have taken many pictures of E. pertinax and have yet to take one that can be identified as E. tenax.
| Date | Sighting |
| 02.07.2004 | On Sedum spectabile in back garden. |
| 21.04.2005 | At rest on South facing cupressus hedge. |
| 26.09.2005 | Basking in full sun on Salix caprea. |
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Hoverfly
Eristalis Arbustorum
.... E. nemorum?
There are a surprising number of hoverfly species and some can look very similar to each other, making positive identification something of a test even for experts. This one appears to be E. arbustorum - but, it might just be E. nemorum.
The prominent 'hourglass' marking on the abdomen would tend to indicate that this is a male. The markings on the females may not be so distinct.
The flies are attracted to the nectar of flowering Cow parsley, Hogweed, Creeping thistle and Knapweed - which give it quite a prolonged season. And in the garden I have seen it on Sedum spectabile and Potentilla.
But, for all that, it is not a common species in my area and I can claim to have seen solitary specimens on no more than six occasions in 2005.
| Date | Sighting |
| 09.09.2005 | On Potentilla in back garden and at rest in full sun on Dogwood. |
Large Narcissus Fly
Merodon equestris
Finding the pupa just below the surface of the soil was a surprise. Given its colour and being covered in crumbs of soil it might easily have been cast aside as just a pebble or compacted soil - but for those two little projecting 'horns'. It was definitely something 'odd'. The image shows the upper and underneath surfaces.
The area that it was found in had been extensively used by mining bees the previous year and I assumed that it might be the pupa of a bee predator but, which one? I took the pupa 'into care' and placed it in a well ventilated container on damp moss - and waited.
Eventually, after five weeks, it hatched and had all the appearance of being a bee but for the absence of typical bee antennae. The very short antennae pointed to it being a 'bee mimic' hoverfly - of which there are several. It normally carried its wings closely folded making it difficult to see any wing vein pattern but I was able to get a good image of an outstretched wing when it started preening itself.
The wing vein characteristics narrowed the species options down to the Eristalini group and eventually to Merodon equestris in particular. Further identifying features were the all black legs and a tiny triangular projection on the hind femur close to the tibia joint (as seen in the lower image) that does not occur in other bumblebee mimics.
The adult fly only survives for a short while - between 5 and 24 days, and lays its eggs low down on the leaves of daffodil, narcissus and bluebell plants. On hatching the larvae make their way down into the bulb where they will feed for something like 300 days before re-emerging to pupate in the soil.
| Date | Sighting |
| 17.04.2008 | Pupa found just below soil level. |
| 24.05.2008 | Adult emerged and released. |
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Hoverfly -
Rhingia campestris
Before I pinned a 'proper' name on this one, I had it labelled as the 'Duck-billed platy-fly'.
The prominent 'snout' forms a protective shield for a long black tongue which is extended (in Bumblebee fashion) to seek out nectar from long tubed flowers - such as White Dead-nettle.
It appears to favour cow pastures as its breeding ground, laying its eggs on plants overhanging cow pats. On hatching, the larvae drop to the dung and burrow to the moist part at the bottom. They feed quite rapidly before the dung dries out, and drop to the grass where they pupate.
It is on the wing from April to November - which roughly equates to the length of time that the favoured White Dead-nettle can be found in bloom in these parts.
It was a chance sighting of the fly on the more open flowers of garden Honesty that revealed the long black tongue in action.
| Date | Sighting |
| 02.07.2004 | On White Dead-nettles in roadside ditch. |
| 21.04.2005 | On White Dead-nettles in roadside ditch. |
| 09.05.2005 | On garden Honesty. |
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Hoverfly -
Sphaerophoria scripta
I would classify these hoverflies as 'unobtrusive'. They are not given to darting about, drawing attention to themselves, but go about their business in a quiet, almost shy manner.
That said, they are not shy when it comes to reproduction. It has been suggested that, given the right environmental conditions (temperature, humidity and food supply), a complete generation can develop from egg to egg laying adult in as little as 16 days. And it is possible for as many as 9 generations a year to appear.
The upper image is of a female. They tend to present themselves in a constant recognisable form.
The lower image is of a male. These can be more variable in colouration and markings but are characterised by their long slim parallel abdomen which will extend beyond folded wing tips.
| Date | Sighting |
| 31.08.2004 | On Potentilla and Thyme in front garden. |
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Hoverfly -
Volucella bombylans
Now this one posed me problems.
The hoverfly in the upper image looks like V. bombylans - but it confused me by behaving like V. inflata - which, I believe, lays its eggs in damp, wet places.
This one spent several leisurely minutes moving over the 'cuckoo spit' on the Fleabane, looking for all the world as though it was ovipositing (which, in retrospect, was highly unlikely since the close spaced eyes suggests that it was a male!). The lower image is that of a female, with widely spaced eyes.
Volucella bombylans, is reputed to favour the dry nests of bees and social wasps for its larvae. Within the bee or wasp nest, the larvae clean up the detrius and waste material in the nest and are rewarded (?) by being allowed to predate on the odd bee or wasp larva!
In order to get away with this behaviour, the fly mimics the bumblebee.
V. bombylans var bombylans (this one) mimics the buff tailed bumblebee.
Whereas V. bombylans var plumata, with a white tail, mimics the white tailed bumblebee.
But we humans are not so easily fooled(?). The bees have four wings and the hoverflies have only two - and their wing venation is very distinctive. The deep 'V' cleft in the wingtip venation is a distinctive characteristic of the Volucella genus and the plumose (hairy) antennae is a key identification feature of this species.
| Date | Sighting |
| 15.06.2004 | On Fleabane in roadside ditch. |
| 29.07.2007 | On garden Lythrum, 'Purple Loosestrife'. |