David
Element
Wildlife
Photography and Digital Video Images
__________________________________________________________________________________________________________ Flies 5 – Ivy Waspgrabbers
IVY WASPGRABBER FLIES Leopoldius signatus (m, f)
IVY WASPGRABBER FLIES
Leopoldius signatus (m, f)
IVY WASPGRABBER FLIES
Leopoldius signatus (m, f)
IVY
WASPGRABBER FLY Leopoldius signatus (f)
IVY WASPGRABBER FLY Leopoldius signatus (f)
- Conopid or Thick-headed flies are
endoparasites of bumblebees and other species of aculeate hymenopterans.
The female conopid grabs a suitable host and injects a single egg between
the body segments, using her powerful and well-armoured ovipositor. In the
case of the nationally scarce Ivy Waspgrabber
Fly Leopoldius signatus,
most readily separated from similar species by the dark markings,
sometimes relatively faintly defined, on the femurs of the hind pair of
legs the unsuspecting victims of L. signatus
are presumed to be Common Wasps Vespula vulgaris. These are grabbed
as they are feeding on the Autumnal bounty of Ivy Hedera helix flowers
– although observing such behaviour in a species that is hard to locate
and surreptitious in its behaviour is difficult to confirm, it is not
known if other vespids are also targeted and the author has never seen
oviposition by this fly. The action must be rapid when it happens and it
is not known if the conopid possesses any defensive mechanisms, a
thickened exoskeleton, for example, to protect it against being stung by
the wasp. It should be noted that the fly exhibits Batesian mimicry,
presumably to deter predation and perhaps also to enable it to approach
its host without alarming it. Pheromonal signals could possibly be
employed for this subterfuge too but this is speculative, and the author
would be interested to hear confirmation of this theory. The larva eats
the non-essential organs and otherwise hijacks the tissues of the
unfortunate host prior to pupation. A detailed account of the fascinating
life-history is given in an article by David Clements, the national
organiser of the British
Conopid Recording Scheme, in "British Wildlife"
Volume 8, Number 5
June 1997. There are 24 British conopid species.
- Further information about this fascinating
fly may be found on Steven Falk’s excellent Flickr site: https://www.flickr.com/photos/63075200@N07/sets/72157678685068204/ .
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