FNZ 32 - Sphecidae (Hymenoptera) - Popular Summary
Harris, AC 1994. Sphecidae (Insecta: Hymenoptera). Fauna of New Zealand 32, 112 pages.
( ISSN 0111-5383 (print), ; no. 32. ISBN 0-478-04534-4 (print) ). Published 07 Oct 1994
On arriving at a holiday home in December, or on returning home after an extended absence, families often find mud adhering to the curtains. When the curtain is pulled, a shower of mud fragments and - good gracious! - limp-bodied spiders descends to the floor.
This is the work of the female of the mason wasp, Pison spinolae, a typical sphecid wasp which builds a nest of mud cells in a sheltered place, often on man-made structures. She provisions the cells with small spiders which she has stung to paralysis, and lays an egg on each one. The tiny larva which hatches from the egg has a ready supply of fresh meat on which to feed and grow.
Other sphecids nest in the ground, forming burrows and nest chambers in sandy or clay soils, according to species. Yet others nest in holes made by wood-boring insects. Tiny sphecids in the genus Spilomena fill borer beetle holes with thrips, and can sometimes be observed resting on the outside of houses.
On the beaches and dunes of northern New Zealand a large red and black sphecid, Podalonia tydei suspiciosa, catches fully grown noctuid moth caterpillars. Having stung one to paralysis, the wasp then straddles it and hauls it to its subterranean nest in the sand.
Throughout the country the shining black Tachysphex nigerrimus is often seen digging holes in sand and fine shingle beside streams, and less often may be observed dragging its cockroach prey across the ground.
The Crabroninae, typically thread-waisted wasps, often prey on flies. The New Zealand species, however, have diverged quite considerably in their prey preferences. One preys exclusively on beetles, another takes only moths, and yet another captures mayflies, caddisflies, and stoneflies in addition to true flies.
For instance, along the Blue Stream at the foot of the Tasman Glacier in Mount Cook National Park, this latter species in January preys exclusively on emerging adult aquatic insects, rejecting seemingly suitable flies even when these would be easy to capture.
This may be an example of the way in which sphecid wasps first come to prey on new orders of insects, and suggests an adaptive capability that would be significant in the evolution of these insects. It also shows shows that field study of New Zealand's sphecid wasps can yield surprising results, as well as fascinating insights into the behaviour of these dedicated hunters.
New Zealand has eighteen species of Sphecidae in seven genera. Nests and adults of a further five species are regularly encountered as importations, but none has so far become established.
Sphecids are solitary or subsocial wasps. The adults are usually active only in sunlight (not on overcast days), and feed largely on plant nectar. Although rather diverse in appearance, resembling variously bees, vespid wasps, or pompilid wasps, the Sphecidae comprise a natural group.