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Southern Riffle Darner Notoaeschna sagittata (Odonata) in the bend of Islands, Victoria.

Introduction

The Southern Riffle Darner Notoaeschna sagittata has been recorded in the Bend of Islands, 30 km north-east of Melbourne. Nine adults and 40 exuviae were found between 25 November 2013 and 23 January 2014. These records, in the Yarra Catchment, are a significant extension to this dragonfly's documented range.

Methods

Sightings were opportunistic, as part of the general Odonata and Lepidoptera observations recorded by the author in the area. When a dragonfly was seen it was photographed if possible. The images were then used to identify the species from Theischinger and Hawking (2006) and various websites. No attempts were made to catch any dragonflies by netting or any other means.

Photos were taken with a hand held Canon Powershot SX20is compact digital camera generally set at x39 (x20 optical and x~2 digital; equivalent 35 mm focal length of 1120 mm), at a distance of 1000 mm minimum. Some exuviae that were an inaccessible distance into the river were photographed through a spotting telescope. Super-macro setting was used to photograph exuviae at close range.

Observations

Adults were seen and photographed by the author nine times in the Bend of Islands. Six adults (three male and three female) were near the banks of the Yarra River. Three adults (two male and one female) with some teneral characteristics, were well away from the Yarra with the minimum distance from the river being up to 1.8 km. The Yarra is the closest viable stream for this species (Table 1 and Figs. 1, 4, front and back cover).

Forty exuviae were also found at seven locations along the Yarra. These were typically on the limbs of dead trees which were partly submerged in the river (Table 1, Figs. 2-4).

An additional sighting has come to the attention of the author. Nick Monaghan photographed an adult 50 m from the banks of the Yarra in North Warrandyte, adjacent to the Pound Bend section of Warrandyte State Park, on 26 December 2012 at 37.731[degrees]S, 145.207[degrees]E. (Nick Monaghan pers. comm. January 2014) This is approximately 7 kms west of the Bend of Islands (20 kms downstream by river) (Life Unseen website at http://lifeunseen.com/index2_item_7308.php).

Discussion

Notoaeschna sagittata is a riverine species and the female is known to oviposit while totally submerged at rapids (Theischinger and Hawking 2006). There are several sections of rapids along the length of river where the observations were made. Despite many hours of watching various rapids on the Yarra, this ovipositing was not observed.

All observed adults were sexed and the sex ratio (five male, four female) was close to parity, recognising the small sample size and odd number.

It is of interest that both male and female adults, with some teneral characteristics, were recorded at least 1.8 km from the Yarra. Theischinger and Hawking (2006: 4), as part of the Life Cycle outline, comment that 'riverine species appear to move only a short distance, up to 500 m from the stream'.

Teneral characteristics were noted on the three adults observed away from the river, but not on the six adults observed near the river. This is consistent with the post emergence strategy of leaving the riparian habitat until maturity. Perhaps this is to avoid the rigours of courtship competition before gaining full strength and ability to deal with the opposition.

There was no obvious correlation between the number of exuviae found at a location and its distance from any of the rapids on the river. Site 5, at which 23 exuviae were found, was about 50 m downstream of a rapid but other trees in similar locations had none. Some locations with exuviae were much further downstream from any rapids, while others were adjacent to rapids.

It is fortunate that N.sagittata exuviae are easily identified, having the epiproct and paraprocts armed with long spines, a spine on the profemur and mid-dorsal spines on abdominal segments 2 to 9 (Fig. 2).

The known range of Notoaeschna sagittata is documented in Theischinger and Endersby (2009). Most Victorian records are in the far east of the state and none in the catchment area of the Yarra River. A number of records since 2009 have been published for eastern Victoria, but none for the Yarra Catchment (Endersby 2014).

Given the proximity to Melbourne, and the number of sightings over a short period, it is surprising that Notoaeschna sagittata has not been recorded previously in the area. 2013/14 may have been a particularly good season. However, the large number of exuviae found indicates that reasonable numbers must have been present in the previous season. The species was not detected, despite regular visits to the area by the author and other known dragonfly enthusiasts over the past few years.

Conservation Status of the Area

In the area of the sightings, the Yarra is flanked by the Bend of Islands on one side and the Mt. Lofty section of Warrandyte State Park on the other. The high quality of the habitat being conserved adjacent to the river will be a contributing factor to the high species diversity in the area. Thirty-two species of Odonata have been recorded in the Bend of Islands by the author since January 2012.

The Bend of Islands is a unique residential conservation area, established in 1976, adjacent to the Yarra River. It is a 634 ha area of high conservation-value bushland, zoned Special Use Zone 2 - Environmental Living (ELZ), in the Shire of Nillumbik. This zoning prohibits the keeping of dogs, cats or other domestic or farm animals, restricts the planting of nonindigenous plants and prohibits the removal of native vegetation without a permit. For more information on the ELZ, refer to the Bend of Islands Conservation Association website at www.bendofislands.wordpress.com. A dragonfly list for the area is included on this website, along with many lists of other flora and fauna. The three observations that occurred away from the Yarra were on, or immediately adjacent to, the Round the Bend Conservation Co-operative. This is a 128 ha property within the ELZ, owned by 32 shareholders, each with a 0.15 ha house site strategically located to minimise impact on the local bushland, which is of State significance, and includes Box-Ironbark Forest (Refer to www.roundthebend.org.au).

Conclusion

Observation of Notoaeschna sagittata in the Bend of Islands is a significant extension of its documented range to include the Yarra catch ment. This demonstrates the positive effect of conservation of remnant bushland close to a capital city.

References

Endersby I (2014) Additional Distribution Records for Victorian Dragonflies (Insecta: Odonata). Victorian Entomologist 43(4), 99.

Endersby I (2014) Additional Distribution Records for Victorian Dragonflies (Insecta: Odonata). Victorian Entomologist 44(2), 36-37.

Theischinger G and Endersby I (2009) Identification Guide to the Australian Odonata (Department of Environment, Climate Change and Water NSW: Sydney)

Theischinger G and Hawking J (2006) The Complete Field Guide to Dragonflies of Australia. (CSIRO Publishing: Melbourne)

Received 13 February 2014; accepted 24 April 2014

Frank Pierce

PO Box 121, Kangaroo Ground, Victoria 3097. Email: jmandfp@bigpond.com

Table 1. Sighting Details of Southern Riffle Darner Notoaeschna
sagittata in The Bend of Islands. (1-) Found by Gavin Masters (2-)
Dead, partly submerged, tree.

Site   Date         Form            Location

1a     25/11/2013   Adult m         Small Wetland
2a     27/11/2013   Exuvia x1       Tree (2) in Yarra
2b     29/11/2013   Exuvia x1       Tree (2) in Yarra
3      7/12/2013    Adult m         House Garden
4a     8/12/2013    Adult f         Bank of Yarra
5a     12/12/2013   Adult m         Bank of Yarra
4b     12/12/2013   Adult m         Bank of Yarra
6a     21/12/2013   Exuvia x1 (1)   Tree (2) in Yarra
7      29/12/2013   Adult f         Bank of Yarra
lb     31/12/2013   Adult f         Small Wetland
8      5/01/2014    Adult m         Bank of Yarra
5b     19/01/2014   Exuviae x14     Tree (2) in Yarra
5c     19/01/2014   Exuviae x9      Tree (2) in Yarra
9      22/01/2014   Exuvia x1       Tree (2) in Yarra
10     22/01/2014   Exuvia x1       Tree (2) in Yarra
11a    23/01/2014   Exuviae x5      Tree (2) in Yarra
11b    23/01/2014   Exuviae x2      Tree (2) in Yarra
11c    23/01/2014   Exuviae x5      Tree (2) in Yarra
12     23/01/2014   Adult f         Bank of Yarra
6b     23/01/2014   Exuvia x1       Tree (2) in Rapid

Site   Distance from Yarra Bank              Latitude   Longitude

1a     Minimum 1.8km to North                37.6861    145.2936
2a     0 m from bank; 1m above water         37.7177    145.285
2b     5 m into river; 1 m above water       37.7177    145.285
3      Minimum 1.4 km to West                37.6893    145.3012
4a     0 m from bank                         37.7163    145.2863
5a     0 m from bank                         37.7145    145.285
4b     0 m from bank                         37.7162    145.2864
6a     0 m from bank; 1.5 m above water      37.7104    145.2835
7      8 m landside of bank                  37.70366   145.2923
lb     Minimum 1.8 km to North               37.6859    145.2939
8      3 m landside of bank                  37.71394   145.28474
5b     6 m into river; 1 m above water       37.7145    145.285
5c     4 m into river; 1.1 m above water     37.7145    145.285
9      6 m into river; 2 m above water       37.71647   145.28615
10     0 m from bank; 1.8m above water       37.71484   145.2859
11a    3 m into river; 1.2 m above water     37.71181   145.28477
11b    1 m into river; 1.1m above water      37.71181   145.28477
11c    1.5 m into river; 1.0 m above water   37.71181   145.28477
12     40 m landside of bank                 37.71266   145.28476
6b     10 m into river; 0.7 m above water    37.7104    145.2835
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Article Details
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Title Annotation:Contributions
Author:Pierce, Frank
Publication:The Victorian Naturalist
Article Type:Report
Date:Oct 1, 2014
Words:1645
Previous Article:A limited vegetation survey of Cocoparra National Park and Cocoparra nature reserve.
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