Southern Riffle Darner Notoaeschna sagittata (Odonata) in the bend of Islands, Victoria.
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.
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.
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).
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).
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.
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
PO Box 121, Kangaroo Ground, Victoria 3097. Email: firstname.lastname@example.org
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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|Publication:||The Victorian Naturalist|
|Date:||Oct 1, 2014|
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