[For explanations and definitions see here. Almost all of the data here is derived from NBN Atlas and the species information from Steven Falk's Flickr and the HRS website]

April is a significant month for hoverflies: Only 11 species are at their peak, but more than 80 are on the rise! It's very much the start of Rhingiini season, with 5 species of Cheilosia at their peak and another 18 getting off the mark, as well as every species in Rhingia, Portevinia and Ferdinandea. Most Pipizines in Pipiza, Herigia and Neocnemodon get going this month too; so make sure you're paying attention to the 'black jobs'.

Advice for getting identifiable pictures of 'black jobs': Some can be identified reasonably easily - but the lack of an abdomen pattern is a hinderance and many realistically require microscopy. Here's how to give yourself the best chance, even with the difficult ones. The face (including side profile), antenna shape and colour, and legs (especially the front tarsi and hind femur) are especially useful. The colour of hairs on the abdomen, scutum, face and legs sometimes play a role - this may be best obtained from the side (or at least not directly from above) so that light shines through the hairs. Wing venation is very useful for getting Pipizines to genus. For Cheilosia small hairs on the sides of the face may be important, and it is often important to know whether the eyes are hairy. For a few Cheilosia (Nr. proxima) it is necessary to turn them over and get the underside of the abdomen (this is also important for tiny Paragus species). If the fly is not in a position to see the underside, catching it in a spi-pot is a useful approach.

April is the best month to see....

*TOP TARGET*

...Platycheirus ambiguus (56,-85%)

A grey-marked Platycheirus, but the only one in which the female is banded rather than spotted, and the only one in which the male foreleg is not expanded in any way (it does have a curled bristle on the back of the front femur near the knee - so try to get one focussed on that knee if you suspect ambiguus. The male frons is very broad and well dusted.

This species is strongly associated with blackthorn. You may see it it hovering near blossoms at 1-4m height. Found throughout Great Britain. Falk's Images

*TOP TARGET*

...Cheilosia nebulosa (65,-76%)

A somewhat furry Cheilosia with a vague dark smudge across the centre and tip of the wing. The colour of the wing bases and scutum hairs can give it a bit of a golden sheen. The frons is rather swollen. The legs are extensively pale, but the femora are black. The antennae are orange, but not excessively bright or large. See Falk's pictures

This species is rather rare but widespread, and can be found in Great Britain as far north as the central belt of Scotland. The specific larval habitat is unknown but the adult is associated with carr (waterlogged woods) and marsh habitats. It can be seen on Salix catkins and hawthorn. If you see it ovipositing that would be amazing - note the plant!

*TOP TARGET*

...Parasyrphus punctulatus (30,-68%)

Our earliest Parasyrphus to peak, and relatively easy to identify. It is best found basking on or hovering near tree foliage - so look up sometimes! Its tastes are wide ranging, but it is usually found in wooded areas, particularly if conifers are present. Throughout Britain and Ireland. Falk's pics

The following species were discussed in March's 'First month you may find', but they peak now:
Cheilosia albipila (44,-79%), Cheilosia grossa (38,-59%), Criorhina ranunculi (35,-71%), Melangyna barbifrons (75,-100%), Melangyna lasiophthalma (25,-81%), Platycheirus discimanus (85,-43%)

Other species that peak in April [species in square brackets usually require microscopy to identify]:
Cheilosia caerulescens (79,+331%), [C. psilophthalma (88,-100%)]

April may be the first month you see...

*TOP TARGET*

...Pocota personata (66,-94%)

43% of peak abundance (%opa) in April. Possibly the best of the bumblebee mimics! Distinctive with its peculiarly small head and droopy orange antennae. A rare species associated with old woodlands and parklands. It seeks rot holes in mature trees, perhaps especially beech, but also Sycamore and Ash. They can easily be mistaken for tree bumblebees entering a high nest. Searching such trees is said to be the best way to find it. Occurs in England as far north as Durham - you might just see one in Wales near the border. Falk's pics

*TOP TARGETS*

...Ferdinandea cuprea (18,-40%) and Ferdinandea ruficornis (65,-100%)

37%opa and 20%opa in April respectively. Ferdinandea are easily recognisable by their metallic sheen, dust-striped scutum, orange antennae, bristly scutum and scutellum margins, and sharply infuscated inner cross veins. F ruficornis is rarer, and harder to confirm from photos. F cuprea has a more golden appearance than the darker F ruficornis; cuprea has small black spines on the backs of the front and middle tibiae - so it's worth trying to get sharp pictures of the legs. In ruficornis the aristae are red rather than black in cuprea - so a sharp picture of the antennae is useful. Falk's images

These are more species associated with trees. The larvae live in sap runs, so woodland with old trees is a good place to look. They may bask on tree trunks. cuprea is common throughout Britain and Ireland.
ruficornis is found in England up to about Leeds, and on the north coast of Wales.

*TOP TARGETS*

...Neoascia interrupta (56,-96%), Neoascia obliqua (49,-95%) and Neoascia meticulosa (27,-95%)

All at 15%opa in April, but obliqua and meticulosa are rising quickly to their peaks in May. These are rather small flies, with abdomens strongly waisted. See Falk's images These are also the three easiest to identify. interrupta and obliqua are amongst the species with infuscated cross veins. interrupta is the only species with lateral spots on T4, obliqua usually has unique, oblique marking on the very narrow T2. meticulosa has very yellow legs. To give yourself the very best chance of identifying the other species of the genus (which all peak in July/August) a sharp side profile of the antennae and the hind knees might get you there. The real clincher is sometimes the underside of the thorax... but this is really hard with such small flies, a spi-pot is your best bet.

In Great Britain meticulosa and obliqua are ubiquitous, but interrupta is basically confined to England with a very small number of extreme outliers in northern Scotland. obliqua is strongly associated with butterbur, meticulosa and interrupta are associated with bulrushes. Falk's pics

...Chalcosyrphus eunotus (60,-95%)

23%opa in April. A well-built and hairy species with infuscated cross veins, most easily confused with Brachypalpus laphriformis, but also easily distinguished by the vague stripy scutum dusting (shiny in B laphriformis) and the grey patches on the second tergite. The larvae develop in partially submerged logs in streams in wooded areas, especially where log jams are formed, and they can be found exploring such logs or basking near the bank on logs or foliage. It is distributed in the west of England south of Liverpool, and the north coast and Marches of Wales. Falk's pics

...Cheilosia pagana (11,-73%)

70%opa in April. Very common, and the female is quite distinctive due to the large bright orange antennae. The male antennae are also orange, but less big and garish! It is important, especially with males, to show that the eyes are not hairy. The face knob is pointed and males lack long white hairs under the hind femur. Most likely to be confused with C soror. Larvae develop in Apiaceae such as cow parsley. Ubiquitous in Britain and Ireland. Falk's pics

...Cheilosia chrysocoma (53,-79%)

26%opa in April. A large and distinctive Cheilosia with dense, long, bright orange hair, orange antennae and infusated cross veins. Associated with damp woodland. Apparently it is most commonly observed resting on low vegetation. Larvae may be associated with wild angelica. Falk's pics

...Meligramma cincta (41,-52%)

48%opa in April. Easily identified by its combination of elongate shape, neat, straight-edged yellow bands, and sharp triangular markings on T2. Only Meliscaeva cinctella is similar, but in that species the T2 markings are blunt and the bands less straight-edged.

It is primarily (but not exclusively) associated with beech-containing woodland (the larvae feed on woolly beech aphids). It will often hover in shafts of light at 2-4m high. Falk's pics

...Parasyrphus annulatus (71,-100%) and Parasyrphus malinellus (63,-100%)

36%opa and 22%opa in April respectively. These two species are certainly rare and neither is yet recorded on iNat. A photo of the face and frons helps confirm the genus. With Parasyrphus, as with Syrphus, it is crucial to get a very clear picture of the hind leg. Hind tibia broadly yellow at the base but not the tip, and hind femur yellow at the base will confirm annulatus (also front tarsi truly yellow and large dust spots on the female frons). mallinellus is most easily confirmed under the microscope but would be confirmed by hind leg all black except broadly at the base of the tibia, front tarsi darker than tibiae, small dust spots on female frons and even better if you can get the small black triangular markings on the underside of the abdomen.

Parasyrphus are usually found in association with coniferous woodland. Records are spread throughout Great Britain. Falk's pics

...Pipiza luteitarsis (49,-86%)

27%opa in April. One of the few relatively easily identifiable species. The entirety of the front tarsi are yellow (in other species at least some segments are black). The body is yellow haired, the wings are clear and, like many other Pipiza, the abdomen often sports a pair of yellow spots.

The larvae feed on the aphid Eriosoma ulmi, which causes leaf curl on elm trees., so look for them near elm (or open the curled leaves and attempt to rear any larvae you find!!). May be found anywhere in Great Britain. Falk's pics

Other species exceeding 10%opa for the first time in April are [species in square brackets usually require microscopy to identify]:

Pipizinae [Heringia heringi (64,-72%) 32%opa]
[Neocnemodon brevidens (90,-100%) 50%opa, N. pubescens (76,-100%) 38%, N. vitripennis (69,-93%) 25%opa]
[Pipiza fasciata (74,-100%) 29%opa, P. lugubris (68,-93%) 17%opa, P. noctiluca (25,-93%) 22%opa, P. notata (51,-100%) 26%opa]
Microdontinae [Microdon mutabilis (50,-94%) 11%opa]
Eristalinae Anasimyia interpuncta (62,-100%) 11%opa
Brachyopa pilosa (54,-100%) 28%opa, B scutellaris (38,-92%) 13%opa
Cheilosia bergenstammi (19,-97%), 34%opa, C, mutabilis (63,-100%) 17%opa, C. variabilis (20,-78%) 16%, [C. antiqua (33,-100%) 11%opa, C. barbata (55,-100%) 19%, C. carbonaria (79,-100%) 20%, C. fraterna (28,-95%) 21%opa, C. griseiventris (73,-100%) 40%opa, C. lasiopa (57,-96%) 11%, C. latifrons (43,-100%) 22%opa, C. proxima (21,-97%) 21%opa, C. pubera (59,-100%) 31%opa, C. ranunculi (61,-100%) 30%, C. semifasciata (42,-100%) 63%opa, C. urbana (53,-100%) 62%opa, C. vernalis (21,-100%) 45%opa]
Criorhina floccosa (31,-62%) 13%opa
Eristalis intricaria (6,-43%) 31%opa, E similis (88,155%) 50%opa
[Eumerus funeralis (34,-96%) 11%opa]
Orthonevra geniculata (45,-98%) 37%opa
[Neoascia podagrica (7,-98%) 15%opa]
Portevinia maculata (23,-66%) 11%opa
Mallota cimbiciformis (56,-92%) 19%opa
Syrphinae Baccha elongata (13,-32%) 19%opa
Dasysyrphus albostriatus (20,+53%) 15%opa, D. tricinctus (24,-45%) 11%opa, [D. pinastri (60,-91%) 20%opa]
Didea fasciata (34,-45%) 15%opa
Epistrophe eligans (10,45%) 51%opa, E. melanostoma (92,+473%) 33%opa
Eupeodes latifasciatus (19,-55%) 16%, E. luniger (8,0%) 49%opa
Melangyna labiatarum (43,-61%) 18%opa, M. sexgutta (=compositarum) (49,-94%) 14%opa
Melanostoma scalare (2,-48%) 52%opa
Meligramma triangulifera (61,-26%) 23%opa
Meliscaeva cinctella (12,-49%) 11%opa
Platycheirus scutatus (14,-84%) 34%opa, P. splendidus (55,-93%) 76%opa, P. sticticus (73,-100%)
40%opa, P. tarsalis (32,-78%) 25%opa
Syrphus ribesii (3,-38%) 28%opa, [S. vitripennis (6,-99%) 15%opa]
Xanthandrus comtus (41,-69%) 10%opa

Posted on February 7, 2024 11:14 PM by matthewvosper