Order MEGALOPTERA

Megaloptera

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Order MEGALOPTERA

Alderflies, Dobsonflies

Compiler and date details

1999 - Updated by A.A. Calder, CSIRO Entomology, Canberra, Australia

1988 - G. Theischinger, Engadine, New South Wales, Australia; W.W.K. Houston, Australian Biological Resources Study, Canberra, Australian Capital Territory, Australia

Introduction

The Megaloptera, commonly known as alderflies or dobsonflies, are mandibulate endopterygote Neoptera with two pairs of wings. Their aquatic larvae are predacious, have well-developed mandibulate mouthparts and lateral abdominal gills and inhabit lotic and lentic environments in tropical and temperate climates world-wide.

The order comprises two families, the Sialidae and the Corydalidae. The latter is divided into two subfamilies, the Corydalinae and the Chauliodinae. The rank accorded these two subfamilies is not settled and they have been used at the family level (Theischinger 1983). Pending a revision of the phylogeny and classification of the Megaloptera of the world, and for the purposes of the this work, we follow the classification adopted by Glorioso (1981) and use these names at the subfamily level.

Megaloptera have long been considered among the most primitive of the endopterygote orders of insects. The earliest records of what are probably primitive Megaloptera are from the Permian. Most recent authors agree that the Megaloptera are the sister group of the wholly terrestrial Rhaphidioptera, which are confined to the Holartic Region and that the Sialidae and the Corydalinae (Corydalinae – Chauliodinae) are sister groups.

Less than 300 species of Megaloptera have been described world-wide. In Australia, 22 corydalids and four sialids have been described. The discovery of only a few more species can be expected. An * placed after the type specimen identifier indicates that the identity of those types has not been confirmed by G.T.

The first species described from Australia was Archichauliodes guttiferus, as Hermes guttiferus, by Walker in 1853. Since then, descriptions of new Australian species were presented in mostly revisional papers by Tillyard (1919), Riek (1954), Kimmins (1954), Theischinger (1983) and Theischinger (1988). The only general accounts of the order in Australia are those of Riek (1971, 1974). Theischinger (1999) has given an inventory and a key to the supraspecific taxa of Australian megalopteran larvae.

The two sialid genera in Australia, Austrosialis and Stenosialis, are considered to be endemic. Of the three Australian corydalid genera, Archichauliodes also occurs in New Zealand and Chile, whilst Protochauliodes is known from Chile and western North America. The western Australian subgenus Archichauliodes (Apochauliodes), now accorded generic rank by Theischinger 1999, some of the species groups of Archichauliodes (as proposed by Theischinger 1983) and all the corydalid species that occur in Australia, however, are endemic. There are no corydalids in Tasmania, whereas there is great diversity of the group in tropical Queensland (13 species).

The Australian Megaloptera are largely restricted to the upper reaches of streams along the Great Dividing Range. Species recorded only from the eastern coastal watersheds may also occur on the headwaters of nearby western rivers; their present known distribution patterns probably reflect the more frequent collecting to the east of the Divide. Within species groups, the distribution of individual species is mostly allopatric on a north-south basis (Watson & Theischinger 1984). Along the Great Dividing Range, the upper reaches of many streams are now in National Parks or in State Forests and the immediate future of species in these areas seems secure. There can be no doubt, however, that human activities, particularly clearing of forests and pollution of aquatic habitats, have been and still are strongly affecting the distributions, especially of some of the more widely distributed species.

BIOLOGY
The life cycle of Megaloptera occupies 1–5 years, with the larvae passing through 10–12 instars (Evans 1984). The adults emerge from late spring to autumn, are short-lived and take little, if any, food. During the day they are usually found resting on vegetation on the margins of larval habitats. Some species fly in bright sunlight, others when the light intensity is low. All Australian species are probably to some extent crepuscular or nocturnal and are attracted to lights.

Copulation takes place on branches or shrubs near the aquatic habitat. Eggs are laid in masses on vegetation or on rocks overhanging or projecting from the water and hatch in 1–4 weeks. The larvae live in spring seepages, streams, rivers, swamps, ponds and lakes and may survive even in temporarily dry streambeds. They feed on a wide variety of small aquatic invertebrates. Pupation occurs in chambers, usually in the soil or in litter, adjacent to the larval habitat. The pupa is active, decticous, exarate and has functional mandibles. The pupal stage lasts only a couple of weeks.

Predators include birds, bats, frogs, fish and other insects. Eggs may be parasitized by Trichogrammatidae (Hymenoptera) and corydalid eggs may be eaten by both adult and larval anthicid beetles.

Acknowledgements

The authors wish to thank Dr J.A.L. Watson for taxonomic advice and for checking the manuscript; Josephine C. Cardale for access to types in the Australian National Insect Collection, Division of Entomology, CSIRO, Canberra; and Dr B.A. Richardson and Dr D.W. Walton of the Bureau of Fauna and Flora for editorial advice.

Database Notes

The information on the Australian Faunal Directory site for the Megaloptera is derived from the Zoological Catalogue of Australia database compiled on the Platypus software program. It incorporates changes made to the work published on 23 December 1988 as (Theischinger, G. & Houston, W.W.K., 1988)

The Megaloptera was updated by A.A. Calder, June 2000.

Limital Area

Distribution data in the Directory is by political and geographic region descriptors and serves as a guide to the distribution of a taxon. For details of a taxon's distribution, the reader should consult the cited references (if any) at genus and species levels.

Australia is defined as including Lord Howe Is., Norfolk Is., Cocos (Keeling) Ils, Christmas Is., Ashmore and Cartier Ils, Macquarie Is., Australian Antarctic Territory, Heard and McDonald Ils, and the waters associated with these land areas of Australian political responsibility. Political areas include the adjacent waters.

Terrestrial geographical terms are based on the drainage systems of continental Australia, while marine terms are self explanatory except as follows: the boundary between the coastal and oceanic zones is the 200 m contour; the Arafura Sea extends from Cape York to 124 DEG E; and the boundary between the Tasman and Coral Seas is considered to be the latitude of Fraser Island, also regarded as the southern terminus of the Great Barrier Reef.

Distribution records, if any, outside of these areas are listed as extralimital. The distribution descriptors for each species are collated to genus level. Users are advised that extralimital distribution for some taxa may not be complete.