COAST - SPIDER-HUNTING WASPS

Spider-hunting wasps (Pompilidae) are covered in full detail in the Lowland Heathland section of the website but there are several species which are commoner on the coast, in the ideal setting of sand dunes. Two of these, found less frequently inland, are Episyron rufipes (14mm) and Pompilus cinereus (12mm).

The female Episyron rufipes, one of the largest of the Pompilids and seen from May to September, has distinct markings with reddish legs and white spots down the flanks - some males (10mm) are all black. The prey is stored on a plant while the nest is excavated in loose sand with the tarsal comb, and is transported to the burrow with typical alacrity, the wasp sometimes employing short flights approximating to jumps.

Pompilus cinereus (10mm) has been very well studied - these details come from Mick Day's monograph on Pompilidae published by the Royal Entomological Society of London.

After catching and paralysing a spider, usually a Lycosid, the female temporarily inters it while she powerfully and quickly digs a burrow nearby. After partial excavation, the spider is carried in and the burrow extended.

The spider recovers partially from the paralysis but is an effective prisoner within the cell. It moves around the confined space and finally is entirely eaten by the wasp larva, but not before it has deposited enough silk to bind the sand grains of the cell wall together, accidentally creating a protective envelope for it and the predator. By comparison with this behaviour, most of the so-called higher fauna, including birds and mammals, seem almost dull in their life cycles.

Pompilus cinereus is one of the species used by Ceropales maculata (10mm). This wasp, sometimes in combination with others of the species, hunts down females of other genera which are transporting their paralysed prey. The host female is driven off and the Ceropales maculata female lays an egg into the lung-book of the paralysed spider. The prey is then left and the host female usually takes it back to the nest. The Ceropales maculata egg hatches first and the larva eats the egg of the host.

At 6-8mm, Agenioideus cinctellus is relatively small. It requires dry situations, does well in sand and is found inland but is strong on the Thames estuary and south coast. Prey usually consists of small jumping spiders (Salticidae) living on vertical faces. Another female, photographed inland, flew for 6cm from a root-plate to a piece of wood jutting out. This behaviour isn't seen often, and not that many Pompilidae are capable of flying with prey anyway.

The prey, common in that location, was a Heliophanus spider taken up (and once down) a vertical face with numerous obstacles in double-quick time. Once during this process the spider was deposited for a couple of minutes while the wasp checked out the nesting site. It was placed on its back and, oddly, the legs were moving, perhaps confirming that Agenioideus cinctellus does not immediately paralyse its prey totally.

Homonotus sanguinolentus (10mm) is a rare spider-hunting wasp found almost exclusively on the coast in Dorset; there is a modern record from Witley Common in Surrey. The wasp, which can have red on the thorax and abdomen but is often entirely black, targets just one species of spider, Cheiracanthium erraticum, which is attacked in the nest.

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.