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 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.

At 6-8mm, Agenioideus cinctellus is significantly smaller than the other two species shown on this page. 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.

Images © Jeremy Early. All rights reserved.

My latest book, My Side of the Fence – the Natural History of a Surrey Garden, was published in spring 2013. Details may be found, and orders placed, via this hyperlink My Side of the Fence.

COAST: Structure . Geese . Wading Birds . Non-wading Birds . Invertebrates . Spider-hunting Wasps . Flora . Purbeck