The Sand Wasp cometh...

When it's sunny, a trip to the sandy areas of the New Forest can be a good way of finding some of the sand-dwelling invertebrates that specialise in using this type of heathland habitat. One example is the Sand Wasp Ammophila sabulosa. In Britain, this is a distinctive genus with a long abdominal petiole (the thin bit) and a blackish and orangey gaster (the widened bit of the abdomen). There are two species, A. sabulosa and A. pubescens - both are fairly common and can be separated by subtle wing-vein variation and by the colour of the tip of the gaster - black in A. pubescens and (as here) blue-black in A. sabulosa. In a global context, care needs to be taken to separate the genera Ammophila and Podalonia, but with so few species in Britain, this is not an issue here.

A. sabulosa at rest on sand, around 20mm long excluding appendages.

As well as being quite spectacular insects, the behaviour shown by females of this genus makes for a fascinating story. The female A. sabulosa makes a short burrow in sandy soil, ending in a single cell - the waste material is spread around to avoid crating a clear spoil-heap that might attract predators. She then hunts for prey some metres around the burrow. This takes the form of large smooth caterpillars, usually of noctuid moths (and rarely sawfly larvae), paralysing them with her sting and carrying them back to the burrow, having memorised its location using small local landmarks. The burrow will soon become a nest for her young, so she can be seen arranging it before dragging the live but immobile prey inside. Once two or three caterpillars have been collected, she lays an egg on one of them. The burrow is then filled in and the entrance obscured by making it appear the same as its surroundings - in North America, females have even been seen using small stones to tamp down the sand in the entrance - a remarkable example of tool use in invertebrates! The larvae, hatching in their hidden nest, are carnivorous and now have a ready food supply once they hatch in a few days' time. Development is rapid with larvae reaching full size in about 10 days, then pupating inside a spun cocoon.

Adults are active hunters and can be seen running quickly across sandy surfaces - making for some tricky photography, but an excellent excuse to look closely at some local heathlands, something well worth doing the next time to sun is shining...

A. sabulosa running on sand, its legs a blur of motion!

References

Baldock, D.W. (2010). Wasps of Surrey. Surrey Wildlife Trust, Woking.
Richards, O.W. (1980). Scolioidea, Vespoidea and Sphecoidea: Hymenoptera, Aculeata. Handbooks for the Identification of British Insects 6 (3b): 1-118.
Yeo, P.F. & Corbet, S.A. (1983). Solitary Wasps. Richmond, Slough.

Zahradnik, J. (1991). Bees, Wasps and Ants. Hamlyn, London.