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Post by nomad on Aug 2, 2016 7:57:21 GMT
Hoverflies.
Introduction.
Many hoverflies are wasp or bee mimics and belong to the family Syrphidae of the order Diptera. Those that study their ecology in some detail are not quite sure how the 'Batesian mimicry', the hypothesis put forward by that great naturalist H.W. Bates works regarding these insects. For some Dipertists have observed that the main predators of hoverflies are not birds but other insects such as spiders, dragonflies, wasps and other Diptera. In the UK, the small bird, the Spotted flycatcher (Muscicapa striata) feeds mainly on species of Diptera including hoverflies but today, sadly this summer visitor to our shores has much declined. It maybe that as hoverflies started to evolve their bee/wasp like markings were to deter the smaller birds that were then their main predators. Scientists put a captive (bred but not tame) Spotted flycatcher in a room with both wasps and hoverflies with similar markings. When the bird caught the wasps, it carefully pulled out the sting before eating them but when the bird caught the hoverflies it just swallow them whole. This clever bird it seems knew the difference between the toxic wasps and its harmless mimic.
In the forward to that wonderful guide ' Britain's Hoverflies ' by Stuart Ball and Roger Morris, their mentor the hoverfly expert ' Alan Stubbs' wrote in his foreword to the book.
" Hoverflies have long been regarded as nice insects, charismatic even. And they get a good press as man's friend, not only because they are colourful and tamely sit on flowers, but because many are useful to gardeners in controlling the numbers of aphids attacking plants".
This year I began photographing these striking insects when I came across them in the field and in this thread I will show you some of my finds and write a little about each species. Most were found in my home county of Wiltshire in England. The identification of the species shown in my images have been validated by Dipterists who know a lot about these insects than I do.
Many species of hoverflies are almost indistinguishable from one another and only by making a reference collection of pinned specimens could your study proceed to an advanced level beyond that of the photographers' lens. In the book mentioned above in a chapter 'Collecting Hoverflies' under a paragraph ' The ethics of collecting' the author state ' it is worth bearing in mind that you will kill many more hoverflies on the front of your car driving to and from a site than you are ever likely to collect'.
Please fill free to add your specimens or Hoverfly images here.
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Post by nomad on Aug 2, 2016 11:06:15 GMT
The Pine Hoverfly, Blera fallax (Linnaeus, 1758).
First up is a real rarity, the pinewood Hoverfly specialist ' Blera fallax'. In Britain this species occurs at only two sites in the Caledonian Pinewoods of the Scottish Highlands where it is listed as Critically Endangered. The larvae which are of the 'Rat tailed maggot' kind feed in rotting cavities of pine stumps. In Northern and Central Europe this species is also regarded as a rarity and the adults are seldom seen. The adults have been observed feeding at wild Raspberry flowers but very little is known about their behaviour. Setting off early for the Laggintal on a fine summer's day, I arrived before most insects were on the wing but one place at the entrance to valley was already in full sunlight. Here I carefully worked along a short bank topped with larch trees and I spotted basking in the warming rays of the sun, this splendid Blera fallax male. I cannot add much about the adults' behaviour because it soon flew off at high speed and I never saw it again or did I find any others. The Lagginthal consists of larch not pine forests, so it is certainly true this species can exist in other coniferous woodland. Near to where I found the Blera fallax, I decided to make my way up through the steep rocky larch woods to some lower cliffs festooned with the bluish fescue grass to look for Erebia christi. Climbing up through the larch woodland, I proceeded with difficulty due to many loose rocks, tall ferns and thorny bramble. Here I did see some large old cut larch stumps, ideal for the larvae of Blera fallax.
Blera fallax male, Lagginthal Valley, 1500 meters. In the Larch forest of the Lagginthal.
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Post by isidro on Aug 2, 2016 16:35:06 GMT
Wowowow! I never heard about this species, was totally unknown to me! It's a real beauty!
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Post by nomad on Aug 2, 2016 19:59:00 GMT
Funny how you know you have found something unusual even when you have never seen one before.
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Post by wollastoni on Aug 3, 2016 9:48:21 GMT
Very nice, thanks Peter.
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Post by nomad on Aug 8, 2016 9:16:32 GMT
Hoverflies of the genus Xanthogramma.
Here are some striking Hoverfly wasp mimic species of the genus Xanthogramma which belong to the sub-family Syrphini. These are fairly small hoverflies reaching 10mm. The larvae are thought to feed on ant-attended aphids within the nests of ants. How the larvae enter the ant nests is not known and why the ants allow their guests to feed on their aphid store and do not kill them remains a mystery. Those Hoverfly species larvae that inhabit ant nests certainly do not resemble ant grubs. All the photographs of these species were taken by myself in England. Xanthogramma citrofasciatum (De Geer, 1776) In the UK this is a rare and localized Hoverfly wasp mimic of Southern England. This species is strongly associated with grassland and open scrub with ant hills of the Yellow meadow Ant, Lasius flavus, though it can apparently use other ant species. The adults tends to bask on low herbage or short turf nearby and males do not show the protracted hovering of the similar X. pedissequum. My own find was a female on Salisbury plain in a grassland scrubby area. Xanthogramma citrofasciatum, Salisbury Plain, Wiltshire May 2016. Xanthogramma citrofasciatum biotope Salisbury Plain. Xanthogramma pedissequum (Harris, 1776). Xanthogramma pedissequum is an uncommon hoverfly that is found in grassland and open woodland rides preferring short turf and some bare ground such as pathways. Most of the records in the UK are from Southern England. The larvae feed on aphids within the nests of Lasius niger ants and probably other species such as Lasius flavus. My finds were in scrubby Cotswold limestone grassland and very surprisingly in an urban Victorian cemetery. Xanthogramma pedissequum, Limestone grassland, Cotswold Hills in the county of Gloucestershire June 2016. Biotope of Xanthogramma pedissequum, limestone grassland, Cotswold Hills. In the old cemetery where I also found Xanthogramma pedissequum there are plenty of 'Yellow Ant' mounds. The old cemetery is surrounded by thousands of houses, a green oasis in a concrete Jungle and is the final resting place of 33,000 of its former inhabitants. I have noticed that Xanthogramma pedissequum fly low to the ground, often between the lower leaves of a bramble or other shrub. Xanthogramma pedissequum Victorian cemetery, Swindon in the county of Wiltshire, July 2016. A Biotope of Xanthogramma pedissequum Victorian cemetery. Ant Hill, Victorian cemetery.
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Post by Paul K on Aug 8, 2016 9:52:21 GMT
"why the ants allow their guests to feed on their aphid store and do not kill them remains a mystery. Those Hoverfly species larvae that inhabit ant nests certainly do not resemble ant grubs." Ants must benefit in some way to allow this to happen. Perhaps they release some source of fluid ants feed on similar to those of Lycaenidae larvae.
Paul
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Post by nomad on Aug 8, 2016 12:48:51 GMT
You are certainly right Paul, the larvae of the hoverfly must be beneficial in some way to the host ants or they would certainly kill them for eating their aphids store. Interestingly, the larvae of Lycaenidae that feed on the actual ant grubs such as M. arion at least looks like them, even though they they grow much larger. The small larvae of the Lycaenidae are carried inside the ant nests, because they have honey glands and the ants know this and tap them when they find them. There is still a lot to be discovered about hoverflies. For instance, it is not known how the larvae of Xanthogramma get inside the ant nests, do the ants bring them in or do the adult hoverfly enter in some way and lay their eggs . If the ants bring them in, then the young larvae must initially feed on something else. I have seen Xanthogramma searching very low to the ground, perhaps seeking out ant nests to lay their eggs in them.
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Post by Paul K on Aug 8, 2016 13:10:23 GMT
Second explanation that I think of is that the ants are fooled by the fly larvae. Even if their appearance is different they may send scent so the ants are actually sure they are one of them and they may even bring in freshly hatched larvae automatically.In this case the adult fly would have to lay eggs very close to the nest entrance. To confirm those theories as you said Peter more study has to be done.
Paul
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Post by nomad on Sept 5, 2016 17:37:43 GMT
Volucella bombylans Linnaeus, 1758. I guess we all have our favourites and although not rare, this is mine as regards Hoverflies. It is the super Bumblebee mimic Volucella bombylans. I found these along a woodland ride and in a clearing in the old forest of Savernake in May and June. There were two forms of Volucella bombylans in the forest, form bombylans, with an orange-red tail, mimicking the Red-tailed Bumblebee ( Bombus lapidarius) and Volucella bombylans form plumata with a white tail, mimicking the White-tailed Bumblebee ( Bombus lucorum) and the Buff-tailed Bumblebee ( Bombus terrestris). The males often sit about on low vegetation and often combat each over in territorial disputes. The female lay their eggs in the bumblebee nests and the larvae are scavengers among the debris at the bottom of the nests and are also predators of their hosts larvae. Volucella bombylans form plumata males.
Volucella bombylans form plumata females. The Bumblebee Bombus lucorum Savernake Forest. Volucella bombylans form bombylans.
Ride Savernake Forest, the habitat of Volucella bombylans.
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Post by mygos on Sept 5, 2016 18:44:00 GMT
Some very nice shots Peter ! Thank you A+, Michel
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Post by nomad on Sept 6, 2016 6:10:50 GMT
Thank you Michel. What an outstanding example of Batesian mimicry evolution has produced in Volucella bombylans. Being quite new to Hoverflies when I first saw these I was amazed, I have to look twice to make sure they were indeed Diptera.
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Post by nomad on Jan 26, 2017 10:22:59 GMT
Sericomyia silentis is a big stocky hoverfly that is a local species, it is usually found in acidic bogs and heathlands, where the aquatic larvae are found in peaty ditches and pools. There is a resident population in Savernake Forest, Wilts, England, the larvae breeding in the small forest ponds and probably in the large water filled ruts left by the Forestry Commission machinery. Sericomyia silentis in Savernake Forest June- September 2016. Top female, bottom male. Male feeding at Ivy flowers
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Post by nomad on Jan 26, 2017 10:36:36 GMT
Leucozona lucorum Linnaeus, 1758. A striking hoverfly with a white band across the upper abdomen and black wing patches. This is a Spring species and it occurs among lush herbaceous vegetation in damp woodland and other well wooded areas. Below . Leucozona lucorum, Battlesbury hillfort near Warminster, West Wiltshire, England. Found among scrub at the bottom of chalk grassland, on the edge of a wood, June 2016. Top male, bottom female.
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Post by nomad on Feb 3, 2017 12:53:03 GMT
Xylota Hoverflies.
lf you are looking for insects in wooded areas including large gardens in the summer months, you are likely to spot the strange Hoverflies of the Xylota genus. The two common ones are Xylota sylvarum with the golden hair apically on the abdomen and Xylota segnis with red segments on the middle of the abdomen. The Xylota hoverflies mimic Spider hunting wasps and Sawflies (Hymenoptera) and are very active insects, running about the leaves of plants and ferns at high speed feeding on microscopic pollen grains. All photographs 2016. Xylota sylvarum. Xylota segnis.
Mimic associations of Xylota segnis.
The spider hunting-wasp Priocnemis perturbator or a closely allied species. The sawfly Macrophya annulata.
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