Revision of the Australian Stephanidae

INTRODUCTION

Taxonomic information on the Australian Stephanidae is very scarce, consisting of isolated species descriptions by a few early authors.^2,3,5,7,9,14 There are no published keys for the identification of these species, and even the genera cannot be easily recognized using the available literature. The Indo-Australian Parastephanellus, redefined in this work, for example, was never clearly separated from the Neotropical Hemistephanus, redefined by Aguiar¹, a problem which still leads authors into misidentifying these taxa.

Biological information for native Australian stephanids is practically nonexistent, except for a note on ovipositional behavior⁸ (Box 1) and a host record⁶, both reported for unidentified species. Nonetheless, significant literature has been generated on an introduced species, the North American S. cinctipes, imported to Tasmania to help control Sirex noctilio (Siricidae), a pest of pine plantations.^{10, 11, 12}

The objective of this study is to revise the Australian Stephanidae, providing keys, illustrations, descriptions and distribution maps for all valid genera and species, and to generate information to help further understand the genus Parastephanellus, a problem taxon in the phylogenetic study of the family (in preparation).

MATERIAL & METHODS

All Australian museums and all major collections in the world were asked for specimens. A total of 300 specimens were examined, including all types, except Stephanus damellicus Westwood (not found). Species were interpreted mainly from females.

Redefinition of Parastephanellus Enderlein

The genus Parastephanellus is currently defined as having a radial cell relatively larger than the median cell (front wing). All other "diagnostic" characters found in the literature for this genus are also shared with Hemistephanus Enderlein. Since the relative size of cells M and R varies, misidentifications are frequent. In fact, Australian species of Parastephanellus have often been described^3,5,7 or identified^4,6 as Hemistephanus.

The following comparative table and illustrations summarize the differences between these two genera, and indicate the apomorphies supporting the genus Parastephanellus. The plus sign indicates the apomorphic state.

Differences between Parastephanellus and Hemistephanus
Parastephanellus	Hemistephanus
1 Pronotal structure simpler	Pronotum highly differentiated
2 Mesonotum transverse	Mesonotum semicircular
3 Setae on M+Cu apical	Setae on M+Cu subapical
4 Veins 2+3Rs and Rs+M fused	Vein 2+3Rs broken basally
5 Pterostigma blunt	Pterostigma acute
6 Apical half 2+3M nebulous	Vein 2+3M entirely tubular
7 Ovipositor sheaths dark	Sheaths pre-apically white

The Australian species of Parastephanellus are usually difficult to differentiate, as most characters of taxonomic importance are not conspicuous, and show a high intra- and interspecific variation. These species share a complex general pattern of cuticular sculpturing, which must be well understood before a meaningful identification can be tried.

Recognition of species is even more difficult with males, for which strongly atypical specimens are not uncommon, and thus sometimes impossible to identify if not associated with the respective females. The collection of mating pairs is of obvious interest, but even these should be carefully studied, as intraspecific mating is not a far-fetched possibility (Box 2).

Diversity, Distribution, and Endemism

Three genera and at least 21 species of Stephanidae occur in Australia: Megischus (2 spp); Parastephanellus (19 spp); and Schlettererius, represented by the imported S. cinctipes.

Number of Species of Stephanidae in Australia.
Genus	Previously known	Undescribed	Endemic
Schlettererius	1	-	-
Megischus	1	1	2
Parastephanellus	5	14	18

The stephanid fauna of Australia, except S. cinctipes, is entirely endemic. The general morphological structure of the species in the two native genera is also fairly characteristic, with subtle, but constant features which are unique for the Australian stephanids, suggesting these species evolved in isolation.

In Australia, stephanids seem to be distributed in two characteristic groups, one on the western side, and one on the eastern side, with no species known from the central part of the country. Only P. rufoornatus occurs on both sides. There are no records of native stephanids in Tasmania.

LITERATURE CITED

1. Aguiar, A. P. Revisão do gênero Hemistephanus Enderlein (Hymenoptera: Stephanidae), com considerações metodológicas. Revta. bras. entomol. (in litt.)

2. Cameron, P. 1905. On some Australian and Malay parasitic Hymenoptera in the museum of the R. zool. Soc. "Natura Artis Magistra" at Amsterdam. Tijdischrift voor Entomologie, 68: 33-47.

3. Elliott, E. A. 1919. Some Undescribed Stephanidae in the British Museum. The Entomologist, 52: 129-131.

4. Elliott, E. A. 1922. Monograph of the hymenopterous family Stephanidae. Proc. Zool. Soc. London, 92: 705-831.

5. Girault, A. A. 1926. A new stephanid from Queensland. Insec. Insc. Menst., 14 (1/3): 16-17.

6. Moore, K. M. 1962. Observations on Some Australian Forest Insects. Proc. Royal Zool. Soc. N. S. Wales, 59: 87-95.

7. Morley, C. 1917. Some Stephanidae: with descriptions of new species. The Entomologist, 50: 105-113.

8. Rodd, N. W. 1951. Some observations on the biology of Stephanidae and Megalyridae (Hym.). Austr. Zool., 11: 341-346; pls. 40-41.

9. Roman, A. 1915. Results of Dr E. Mjöbergs Swedish Scientific Expeditions to Australia 1910-13. 1. Schulpfwespen. Ark. Zool., 9 (9): 1-3.

10. Taylor, K. L. 1967a. Parasitism of Sirex noctilio F. by Schlettererius cinctipes (Cresson) (Hymenoptera: Stephanidae). J. Austr. entomol. Soc., 6: 13-19.

11. Taylor, K. L. 1967b. The introduction, culture, liberation and recovery of parasites of Sirex noctilio in Tasmania, 1962-67. CSIRO. Division of Entomology Technical Paper No. 8. 19pp.

12. Taylor, K. L. 1981. The Sirex woodwasp: ecology and control of an introduced forest insect. Pages 231-48 in R. L. Kitching and R. E. Jones (eds), The Ecology of Pests. Some Australian Case Histories, 254 pp. Melbourne: CSIRO.

13. Vincent, D & J. D. Hoffman. 1974. Advantages of using fluorescent light with dissecting microscopes in taxonomic investigations. Ann. Ent. Soc. Am., 67: 820-1.

14. Westwood, J. O. 1874. Thesaurus entomologicus Oxoniensis; or, Illustrations of new, rare, and interesting insects... with forty plates from drawings by the author. Clarendon Press, Oxford. 205 pp., 40 pl.

BOX 2A. Hybrid Holotype?

No specimen was found to match the holotype of P. pictipes, which is, however, a clear intermediate between P. albiceps Elliott and P. rufoornatus (Cam.) [See table below]

Hybrid (?) characters in the holotype of P. pictipes Roman.
Typical for P. rufoornatus	Typical for P. albiceps
Hind coxa short	No yellow marks on face
Hind femur short and wide	Temple short
Pygidial sulcus deeply notched	Scutellum punctate-foveolate
Pterostigma apically blunt	Propodeum with large areolations
Gaster long	-
Overal size small	-

The observed hind leg proportions are incompatible with those of P. albiceps, but typical for P. rufoornatus. The long gaster, similar vertex/temple sculpturing, and small size, are also characteristic of P. rufoornatus. However, crucial diagnostic characters of this species are "replaced" by typical characters for P. albiceps, as the strong sculpturing of the scutellum, unicolor face, narrow gena, etc.

This strong ambiguity, and the absence of similar specimens, make it unlikely that P. pictipes is either a synonym or a distinct species.

One possibility is that this holotype is a hybrid of the two species discussed above. This is at least geographically and morphologically possible, as these species are sympatric and share structurally identical genitalia.