The Water Beetles of Scott Creek Conservation Park Scott Creek in December. Photo : Lars Hendrich  


Extracts from a paper
by Dipl.-Biol. Lars Hendrich

A pool in Scott Creek, near Mackereth Cottage
 


INTRODUCTION

Invertebrates (ants, aquatic beetles and jewel beetles) were sampled by Archie MacArthur (South Australian Museum, Adelaide), Lars Hendrich (Free University of Berlin, Germany), Stephan Gottwald (Berlin, Germany) and Tom Hands (Friends of Scott Creek Conservation Park, Adelaide) during two one day field trips in December 1999 in Scott Creek Conservation Park. Previously the park has not been well investigated for invertebrates, therefore the study provided some interesting regional records.


Water beetles are an important animal group in Australian freshwaters. In wetland management, water beetles prove to be an important biomonitoring group. They inhabit virtually every kind of fresh- and brackish water habitat, from the smallest puddles up to large lakes and swamps and from streams to irrigation ditches and reservoirs. Due to their diversity in terms of species numbers, variation in size and ecological niche they represent an ideal group for environmental impact assessments (ElAs), conservation assessments and biodiversity studies in a wider sense (WATTS, 1989).

Hopefully the present report will prove useful for conservationists monitoring the biological health of freshwater habitats in the park.

COLLECTING PROCEDURES
Most of the specimens were collected using different kinds of aquatic dip nets and metal kitchen strainers Diameters of meshes varied from 500 to 1000 microns. Leaf litter and aquatic vegetation were swept heavily; the material obtained was then placed on a white 1m x 1m nylon sheet. Specimens were sorted with forceps and/ or an aspirator.

Less active species or individuals were traced by carefully sorting the substrate. Beetles from springs, small puddles and streams can frequently be directly sampled with an aspirator or a pair of forceps. Specimens of Hydrophilidae and Hydrochidae were collected by washing leaf litter and grass mats at the edge of a water body. The beetles, which usually cling to the substrate, are thus released and float on the water surface, where they can then easily be picked up with an aspirator.
   
An almost dry creek bed. Photo : Lars Hendrich
 

The exposed, swampy and shallow puddle of an almost dry creek - completely covered with Juncus and mats of floating grass. This is the habitat of Platynectes reticulosus, a predaceous water beetle.

 

 

LOCALITIES SAMPLED
Field work was carried on 13th December 1999 and 18th December 1999. The survey area of this study included most aquatic habitat types of the park. The dominant habitats in the park are intermittent creeks and old farm dams and ponds, often with acidic water. In winter and spring temporary and shallow pools in heath- and grassland may exist. Those sites appearing to be of particular interest for the likelihood of finding interesting species were most intensively sampled.

Swampy shallow puddles are home to Platynectes reticulosus. Photo : Lars Hendrich  

THE SPECIES AND SPECIMENS COLLECTED
The predominant family in the park are the predaceous water beetles or Dytiscidae. According to MATTHEWS (1980) 44 species are reported from the State. That means around 40 % of the South Australia's Dytiscidae are living within the park.

The majority of the species recorded so far (22 out of 25 species) are widely distributed in south and south eastern Australia, including Tasmania. Just two species (Platynectes decempunctatus and Hyphydrus elegans) occur in most parts of Australia. At least Rhantus suturalis is widespread in the Palaeartic, Oriental and Australasian realms.

The greatest diversity was met in a Blackwater Dam... This old farm dam held 15 species including a population of the largest (over 3 cm) predaceous water beetle of South Australia, Onychohydrus scutellaris.

The other interesting water beetle is Haliplus australis, a species with low population density and rarely collected in South Australia.

The habitat of Platynectes reticulosus.  

Of the 25 species recorded here, 6 species are restricted to standing waters (lentic sites), while only one species, the whirligig Macrogyrus angustatus, is found in lotic situations only.

However, in some cases this division is difficult as different habitats often merge into one another, especially in the dry summer period when the study took place, and many creeks and small streams started to drawn. A good example is the predaceous water beetles Platynectes reticulosus and Necterosoma dispar, in which larvae and adults occur in stagnant rest pools of intermittent creeks, as well as in slow flowing permanent streams.

Necterosoma dispar (Germar, 1848). Photo by author.
Sternopriscus clavatus (Sharp, 1882) Photo by author.
Deep black water pool, habitat of Sternopriscus clavatus and Onychohydrus scuttellaris.  Photo : Lars Hendrich

At least 18 species were found in both lotic and lentic habitats. Seven species occur in permanent and temporary habitats and 18 species are restricted to more permanent water bodies. (There is a full list available).

The list of the aquatic beetles of Scott Creek Conservation Park is far from being complete. No temporary puddles or pools have been sampled during the short fieldtrip. So there is no doubt that further studies in winter and spring will reveal additional species.


ACKNOWLEDGEMENTS
The author is grateful to Archie MacArthur, Tom Hands and Stephan Gottwald for their assistance and enthusiastic encouragement in the field. DR Chris H. Watts is warmly thanked for an invitation to South Australian Museum (November-December 1999) under financial support of the "Museum Board Fellowship" where this work was initiated.

 

Dipl.-Biol. Lars Hendrich, Moerchinger Strasse, 115 A D-14169 Berlin, Germany (e-mail hendrich1@aol.com)

 

A half shaded permanent and deep blackwater pool. A shallow bay rich in aquatic vegetation, rotten leaves and twiggs. Habitat of Haliplus australis, Sternopriscus clavatus and Onychohydrus scutellaris.

All habitat photos by Lars Hendrich. Stephan Gottwald (Berlin, Germany), who assisted in the collection, also took some excellent pictures of the Jewel Beetles commonly found in the Park.

 

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