Cerceris arenaria and Cerceris rybyensis are parasitised in particular by Hedychrum nobile (8mm), a cuckoo wasp added to the British list relatively recently. They are now two a penny in many sandy parts of lowland England though that phrase hardly does justice to a species which is one of the most attractive of its kind, with the female showing a mixture of colours and the male just two. For the record, accurate descriptions of the colours are virtually impossible since light refraction turns blue to green and back, and makes red vary significantly too.
Hedychrum nobile is one of around 40 British species of Chrysid or ruby-tail wasp, some of whom are cleptoparasites feeding on the food stored in the host's nest and some parasites feeding on larvae. They are heavily armoured for protection and, additionally, the majority can adopt a rolled-up defensive posture when threatened. Males are much less often seen than females.
Hedychrum nobile's methods are typical. Bright sunshine is ideal for them, principally in July and August. I watched a female take a quarter of an hour checking out 14 burrows along a fairly small section of sand. On one occasion she met another of her kind exiting and on another she was faced off by a Cerceris arenaria in the nest. Eventually she found a free burrow and set about her work, which took several minutes.
One of a different family that parasitises Cerceris species among others (also including spider-hunting wasps and mining bees) is the scarce Smicromyrme rufipes, a tiny wasp (6mm) to be dealing with such a large set of hosts. They are from the Mutillidae or Velvet Ant family, which sees the females wingless and the males able to fly. The female lays her eggs on mature larvae, meaning her progeny eats the host rather than the food provided for it. Much of their time is spent running quickly across the ground seeking likely nest sites to enter. The pictured female was in no danger from the adjacent Cerceris rybyensis head as the latter was detached.
Satellite flies (Metopia sp, 6mm), from the Miltogramminae family, tend to follow the wasp back to a nest and then take their chance. Their vulnerability is counteracted by alertness, speed and the application of larviposition, whereby their eggs hatch into maggots as soon as they are deposited. Other flies from the family, including Miltogramma punctata (6mm), parasitise a variety of aculeate hymenoptera, usually solitary bees. However, the pictured fly spent some time lurking near a Cerceris arenaria nest and eventually went into it.
Images © Jeremy Early. All rights reserved.
In 2013 I published My Side of the Fence - the Natural History of a Surrey Garden. Details may be found, and orders placed, via this hyperlink My Side of the Fence. In November 2015 Surrey Wildlife Trust published the atlas Soldierflies, their allies and Conopidae of Surrey, jointly written by David Baldock and me. Details are on this web page: Atlas.