FNZ 12 - Pompilidae (Insecta: Hymenoptera) - Nesting Behaviour
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
Morphology and behaviour are closely interrelated in Pompilidae, as they are in most aculeate Hymenoptera, and taxonomists ever since Linnaeus have sought to include ethological notes in their descriptions of wasps, bees, and ants. In an excellent study on the classification and phylogeny of the social Vespidae, Ducke (1914) made extensive use of nesting behaviour. Wheeler (1923, 1928) undertook similar studies on ants; Plath (1934) proposed a classification of bumblebees based on nesting behaviour; Duncan (1939) showed a close parallel between morphological and biological characters in defining the genera of Vespidae; Spooner (1948) found clear-cut generic and specific differences in the behaviour of the British Pseninae (Sphecidae); and Michener has made comparable discoveries with solitary bees. Evans (1953) constructed a classification of Pompilidae based solely on their comparative ethology, and this very closely paralleled the existing morphological one. Hence, nidification cycles provide revealing taxonomic characters that should be used in classification to support conclusions derived from morphology.
Comparative ethologists of solitary wasps such as Iwata (1942), Arens (1948), Tsuneki (1957), Evans (e.g., 1958), Olberg (1959), Malyshev (1966), and Grandi (1971) have divided the nesting cycles into behavioural sequences which are denoted by letters and numbers. Harris (1974) applied the nesting formulae devised by Arens (1948), Malyshev (1966), and Evans & Eberhard (1970) to the New Zealand species. Nidification formulae based on such sequences are usually arranged in hierarchies ranging from simple to complex. It is frequently assumed that simple nidification formulae represent a lower stage of evolutionary development than more complex ones.
Priocnemis (T.) monachus usually performs the full set of sequences devised by Malyshev. Not all species do this, however, and many enact the steps in a different order. For example, a more derived species may dig a cell before it hunts a spider, whereas a primitive one often digs its cell after it has captured a spider.
|Behavioural sequences (after Malyshev l966)|
|ai||seeking the victim|
|aii||attacking and paralysing it|
|aiii||transporting it to a particular place for temporary keeping|
|B||preparation of the nest|
|bi||seeking a place for the nest|
|bii||digging the nest, repairing, etc., usually combined with visiting the prey|
|C||transporting the prey to the nest and installing it|
|ci||dragging the prey to the nest|
|cii||inspecting the nest|
|ciii||dragging the prey into the nest|
|E||closing the nest|
|ei||closing the cell|
|eii||closing the nest|
Evans & Eberhard (1970, pp. 114 - 119) gave a simplified nesting hierarchy which is used in this account. Only the first four stages apply to Pompilidae, as follows:
- prey - egg
No nest made; egg laid directly on host - e.g., Epipompilus insularis.
- prey - niche - egg - (closure)
Prey caught outside its own burrow and dragged back into its burrow - no New Zealand examples.
- prey - nest - egg - closure
Prey dragged into pre-existing hole which may subsequently be modified by the wasp; prey caught before nest is made or found - e.g., all species in New Zealand (except E. insularis); always in Priocnemis nitidiventris, which seemingly makes only single-celled nests exclusively in sand; sometimes pnly in the other species.
- nest - prey - egg - (cell) - closure
Multi-celled nests made in soil with cells branching from a main burrow, or a series of cells in wood, separated by mud partitions; nest made before prey is caught - e.g., all species in New Zealand (except E. insularis and P. nitidiventris), sometimes.
4a. Prey caught before terminal spur enlarged into cell - e.g., P. monachus (sometimes), P. conformis (ocasionally), P. ordishi n.sp., P. carbonarius (sometimes), P. crawi n.sp. (sometimes).
4b. Nest cell prepared before prey caught - e.g., Cryptocheilus australis, sometimes.
Other aspects of the life cycle provide valuable taxonomic characters. For example, the manner of prey carriage (Figures 170 - 175) is sometimes of use at the specific and generic levels, and the position of the egg on the spider (shown, inter alia, in Figures 177 - 202) and the effects of the pompilid's venom are sometimes useful for distinguishing species. Similarly, the types of prey taken have taxonomic significance. Evans (1959b) found that the genera Poecilopompilus, Batozonellus, and Episyron, which are very similar in both adult and larval characters, all use Epeiridae as prey. Evans & Yoshimoto (1962) and Kurczewski & Kurczewski (1968a, b, 1972) found Priocnemis to take errant hunting spiders; the first-named authors used this fact in their ethological diagnosis of the genus. In this light it is interesting that two New Zealand Priocnemis (Trichocurgus) species, monachus and conformis, prey mainly on mygalomorph spiders.
The New Zealand Pompilidae are extremely varied in their nesting behaviour, ranging from a species that does not make nests (Epipompilus insularis) through mud-daubing, tree-nesting species (Sphictostethus fugax) to species that dig compound nests (e.g., Priocnemis (T.) carbonarius) which may be used by many generations over several years (e.g., P. (T.) monachus).
The terminology applied to nest structure is illustrated in Figure 176, and representative nests are shown, inter alia, in Figures 177-202.