FNZ 12 - Pompilidae (Insecta: Hymenoptera) - Introduction
Harris, AC 1987. Pompilidae (Insecta: Hymenoptera). Fauna of New Zealand 12, 160 pages.
( ISSN 0111-5383 (print), ; no. 12. ISBN 0-477-02501-3 (print), ). Published 13 Nov 1987
The family Pompilidae (spiderwasps) comprises long-legged, solitary wasps that provision their nest cells exclusively with spiders. The females can often be seen during summer running rapidly over the ground, with their wings periodically flicking, as they search for prey. Most will cease activity whenever a small cloud causes a shadow, for heliotaxis (requiring sunlight for movement) is a characteristic of the family.
Pompilidae characteristically use a single prey item to provision each nest cell; the paralysed spider is dragged backwards across the ground; the female uses the apex of her abdomen as a trowel and as a hammer during preparation of the nest burrow; and usually (and in contrast to most other wasps) the prey is caught before the nest is prepared. However, New Zealand species variously do not exhibit one or other of the last three traits, although the first one always applies. Some overseas species are said to be host-specific, but New Zealand's pompilids take a range of prey species and hunt by habitat.
Adult pompilids are distinguished from most other wasps by the presence of a single, straight, transverse groove that divides the mesopleuron into upper and lower halves (see Figure 8); the larvae differ from those of many other solitary wasps in having the second pair of thoracic spiracles greatly reduced.
The family has long been in need of revision. Hitherto, descriptions had been based either on single specimens or on very small series, and a number of nominal species had been erected without comparison with previously described species. As colour variation is very marked, involving both body pigmentation and banding and infuscation on the wings, it is not suprising that many synonyms have arisen.
This contribution is an abridgement of Harris (1974), which was a first attempt at revision of the New Zealand Pompilidae, based on three seasons intensive collecting and observation in the field. From November 1971 to April 1972, and from September to April of 1972-73 and 1973-74, I collected some 30 500 pompilids around New Zealand, from Cape Reinga to southern Stewart Island. To these were added the relatively few specimens contained in the country's main insect collections. For transport I used a 180 cc motorscooter fitted with additional carrying bags. This enabled me to operate from a tent, servicing Malaise traps, observing adult wasps, and checking larvae developing in pots within improvised cages, over a radius of about 450 km. After 1 - 3 weeks in an area a new site would be selected. Routes taken and major collecting stations are mapped in Harris (1974, appendix figure 01).
It became apparent to me during this study that in the Pompilidae behaviour, morphology, and ecological niche are closely interrelated. For many taxa, consequently, behavioural studies have facilitated accurate taxonomic interpretation of morphology, especially where convergent evolution is involved. Similarly, comparative larval morphology has provided a check on the classification based on adults.
Three facts were fundamental to my assessment of the taxonomic standing of geographical isolates and colour forms, many of which had been named: (i) in four species melanism varies clinally from Spirits Bay (34°27'S) to southern Stewart Island (47°16' S) in relation to climatic factors; (ii) varying degrees of melanism can be induced in some species (but not in others) by lowering the temperatures experienced by the pupa; (iii) disruption in the clines occurs at the sites of past and present geographical barriers.
An understanding of mimicry complexes has provided a further insight into some patterns of geographical variation.
It has been deeply rewarding to discover for myself that a seemingly complex taxonomic picture is amenable to simplification by way of intensive, regionally representative study in the field. An holistic approach to insect systematics appears to offer insights that may not emerge from studies based on the narrower view of comparative morphology alone. Many professional systematists - perhaps most - are unable to spend months at a time in the field, from year to year, gathering study material and observations that will enable them to piece together a composite view of a taxonomic group. Probably this situation will not change much, and this highlights two very important needs: the need for meticulous recording of biological data in support of specimens taken from the field; and the need for close co-operation between those who hold specimens and data and those wishing to study them.
Type specimens of almost all New Zealand species are in the British Museum (Natural History), where Mr M. C. Day has made comparisons between them and typical specimens sent to him. The holotype of Sphex nitida Fabricius, 1775 has been lost; the type material of Agenia brownii Gribodo and Cryptocheilus australis Halliday is in the Museo Civico di Storia Naturale "G. Doria", Genoa (in good condition); and the syntype series of Epipompilus insularis Kohl is in the Naturhistorisches Museum, Vienna.