Sand Wasps | Small World Discoveries

HYMENOPTERA | Stinging Wasps

Sphecidae (Sand Wasps)

With most of the former members of this family being incorporated into the Crabronidae, the current British List now includes just four sphecid species; two Podalonia genus coastal sand wasps that are rare or nationally scarce, and two very similar Ammophila species that can be found on dry heathland.

Ammophila pubescens

Heath Sand Wasp

Ammophila sabulosa

Red-banded Sand Wasp

Of the two species, Ammophila sabulosa is by far the more common and widespread, whereas Ammophila pubescens is restricted mainly to southern counties with most records from Surrey, West Sussex, Hampshire and East Dorset.

Both species have a black head and body, a long and narrowed 'waist' (petiole), and an abdomen with an orangy-red band. The tip of the abdomen is black, although in bright sunlight it appears to have a bluish sheen. The legs are long.

Ammophila sabulosa is slightly larger with a body length of 14-24mm and, according to some descriptions, can be separated from Ammophila pubescens, which averages 13-19mm, by its 'waist' that widens more gradually. Personally, I'm not too sure how useful that is unless you had both specis next to each other. For proper identification you need a clear view of the forewing submarginals to see if cell 3 is stalked, in which case it would be Ammophila pubescens, but if it makes broad contact with the marginal cell in front, it would be Ammophila sabulosa. Unfortunately, due to a combination of focus angles and light reflection, it's not always possible to determine. Having said that, I've been able to positively identify every individual I've photographed except one, as usually there's at least one shot from any particular sequence of photos that shows the cell connection.

The following photos were taken on my local heath where we have both species. They look so similar, but by carefully examining the wing cells you can see they are different species. Admittedly, the stalked cell on the left-hand photo of Ammophila pubescens is clearer than the broad connection of Ammophila sabulosa on the right but, when I look at that photo on a large screen together with others from the sequence, I can clearly see the detail I'm after.

Ammophila pubescens

Holt Heath, East Dorset | Aug.21

Ammophila sabulosa

Holt Heath, East Dorset | Aug.21

Although both wasps can often be found hunting and nesting in the same vicinity, it’s interesting to note that they have very different strategies for maintaining and provisioning their nests.

Ammophila sabulosa females adopt the conventional approach where they prefer to provision each nest cell with a single suitably-sized paralysed caterpillar that often requires dragging back to the burrow. There could be up to ten nests and some may be stocked with a number of smaller caterpillars, but the egg would only be injected into one. Once all the cells are provisioned and the eggs injected, the burrow entrance would be sealed with small stones or twigs and then covered with sand, which is what the individual in the left-hand photo below has just done. Ammophila sabulosa has also been recorded parasitising their own species, either by stealing prey from another female’s nest or by substituting that female’s egg with one of their own; a practice known as brood parasitism.

Ammophila sabulosa

Holt Heath, East Dorset | Aug.21

Ammophila sabulosa

Slap Bottom, Burley, New Forest | Aug.21

Ammophila pubescens on the other hand practices a somewhat different approach where the nest cells are usually provisioned with a smaller caterpillar. The female injects her egg and then, rather than providing more food for her larvae before the egg hatches, she will temporarily seal the entrance. Further burrows would be dug and provisioned in a similar manner, during the process of which the female would go back and open nests to see if her eggs had hatched. If her inspection revealed a larva, she would go on to provision the cell with more caterpillars. Further checks would be made of each cell to ensure that all the larvae were properly provisioned before the burrow was finally sealed.

I watched the female in the two photos below taken on Slepe Heath do exactly that. She cleared the first burrow entrance of small stones, clearing them to one side, then quickly checked inside before resealing it. She then uncovered another burrow entrance hidden nearby and went through the same process.

Ammophila pubescens

Slepe Heath, Isle of Purbeck, Dorset | Aug.21

Ammophila pubescens

Holt Heath, East Dorset | Aug.21

Ammophila pubescens

Slepe Heath, Isle of Purbeck, Dorset | Aug.21

Ammophila pubescens

Holt Heath, East Dorset | Aug.21