Buprestidae of South Australia
( Jewel beetles )
by Peter J. Lang
Melobasis soror soror   Blackburn, 1887
subfamily  Buprestinae » tribe  Melobasini » subtribe  Melobasina
Melobasis  species group: nervosa
Melobasis soror soror   Adult images
Melobasis soror soror, PL0698, male, on Senna artemisioides ssp. petiolaris, MU, 11.6 × 3.7 mm Melobasis soror soror, PL0698, male, on Senna artemisioides ssp. petiolaris, MU, 11.6 × 3.7 mm Melobasis soror soror, PL0698, male, MU, 11.6 × 3.7 mm Melobasis soror soror, PL0698, male, on Senna artemisioides ssp. petiolaris, MU, 11.6 × 3.7 mm Melobasis soror soror, PL1540A, on Senna artemisioides ssp. petiolaris, EP Melobasis soror soror, PL1540A, on Senna artemisioides ssp. petiolaris, EP Melobasis soror soror, PL1540A, on Senna artemisioides ssp. petiolaris, EP Melobasis soror soror, PL0698, male, on Senna artemisioides ssp. petiolaris, MU, 11.6 × 3.7 mm Melobasis soror soror, PL0698, male, on Senna artemisioides ssp. petiolaris, MU, 11.6 × 3.7 mm Melobasis soror soror, PL0698, male, on Senna artemisioides ssp. petiolaris, MU, 11.6 × 3.7 mm Melobasis soror soror, PL4911A, female, on Acacia calamifolia (PJL 3526), FR, 14.3 × 4.7 mm Melobasis soror soror, PL4911A, female, on Acacia calamifolia (PJL 3526), FR, 14.3 × 4.7 mm Melobasis soror soror, PL4911A, female, on Acacia calamifolia (PJL 3526), FR, 14.3 × 4.7 mm Melobasis soror soror, PL1540, adult host plant, Senna artemisioides ssp. petiolaris, EP Melobasis soror soror, PL1540, adult host plant, Senna artemisioides ssp. petiolaris, EP Melobasis soror soror, PL4911A, adult host plant, Acacia calamifolia (PJL 3526), FR, 14.3 × 4.7 mm Melobasis soror soror, PL4911A, adult host plant, Acacia calamifolia (PJL 3526), FR, 14.3 × 4.7 mm
Actual
size¹:
12.9 mm
×
4.2 mm
Measurements (mm)
malefemale
L112.5
11.6 – 13.4
n = 1513.2
11 – 14.25
n = 15
L212.3
11.6 – 13.1
n = 1412.8
10.6 – 13.9
n = 14
W4.0
3.2 – 4.3
n = 154.4
3.6 – 4.75
n = 15
Legend  L1length from clypeus/frons to elytral apex (mean, range, sample size)
L2length from anterior of edge of eyes to elytral apex
Wmaximum width with elytra fully closed
Melobasis soror soror  Distinctive features

Pronotum strongly rounded at the sides and tapered towards its base; elytra with 1 to 2 very shallow to weakly defined abbreviated ridges (not reaching base), and suture raised in its posterior half; silvery-white hairs dense on frons of head, and mid-dense on much of the ventral side; ‘prosternum gently and shortly bent over or depressed along its anterior margin’ (Blackburn 1887). The body shape is more slender (narrower and thinner) than in M. rothei and the silvery hairs more conspicuous. Differs from M. nervosa in SA by its much reduced elytral ribs, smaller size and different aedeagus. Readily distinguishable from M. sordida by the puncta of the medial pronotum not being transversely elongated.

Notes

Blackburn 1887 described Melobasis soror from an insect he received from 'Mr. Rothe of Sedan', along with 'several specimens in the South Australian Museum devoid of any record of capture'.

Previously this species had been often misidentified in SA as Melobasis rothei, and it was included on these pages under that name until November 2020. However, in the key to species groups of Levey 2012, M. rothei is in the M. melanura group, whereas this species clearly belongs in the M. nervosa species group.

Using the key in the revision of the M. nervosa species group by Levey 2018, I determined my collections as being closest to the endemic WA species M. barkeri but differing in several features. This view was supported by Levey (pers. comm. Jul. 2020) who regarded it as 'probably an undescribed species' based on a specimen image I sent to him. Consequently, it was treated on this website as Melobasis sp. Senna from November 2020 to December 2023.

I was baffled by M. soror being a long-established and widely distributed SA species that I had seemingly not encountered. In December 2023 I undertook a critical examination of the two old and darkened paralectotypes, which, along with four other SA specimens at the SA Museum (two old and two more recent), had determinations as M. soror made by Brian Levey in 1983 or 1984. All were found to display the salient features in Blackburn’s description, and the two more recent collections also closely resemble M. sp. Senna in coloration and surface texture. Furthermore, the aedeagus on specimens of M. sp. Senna in my collection displayed the key features described and illustrated for M. soror in the Levey 2018 treatment. It became clear that M. sp. Senna was synonymous with M. soror, and more particularly with subspecies soror of Levey 2018.

A contributing factor to the past confusion is the rather atypical specimen from Beverley in WA used to illustrate the habit of M. soror soror in the treatment of Levey 2018. It differs from SA specimens by its shorter shape, and it appears to have more prominent ridges on the elytra than the very subtle ones usual in SA. Levey compared M. soror to the prominently ribbed M. nervosa, stating that subspecies soror looked ‘very like small specimens of M. nervosa which might be the most closely related species', and was 'easily distinguished from this species by the form of the aedeagus'. Blackburn 1887, considered M. soror as 'somewhat allied to M. nervosa' and emphasised the reduction in number and prominence of elytral ridges.

Distribution
SA Regions¹:  FREPNLMUSL
Australian States:  WASAVIC
Southern South Australian occurrences
LegendP.J.Lang collection vouchered records
other private collection or museum specimens, or sightings
Satellite map
Terrain map
Enlarge map
Adult activity records for Melobasis soror soror  (total of 51 beetles)
1 7 5
11 6 3
18
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
Legend
live emerged adults, count > median value of 6 per quarter month
live emerged adults, count <= median value of 6
live non-emerged adults only, for that quarter month
12
number of active beetles for that quarter month
Adult host plants
beetles sites SA regions¹ family position on host plant
192FR, EPF
105EP, MUF
95EP, MUF
Senna artemisioides83MUF
22MUF
Senna sp.22EPF
21EPF
Legendbeetlescount of beetles collected from, or sighted on, host plant taxon
sitescount of major sites (unique 10 km grid cells +/- some distinct approximate localities)
Plant names in green are hyperlinked to a matching host species page with plant photos.
Plant family
Code beetles % host plant taxa
F Fabaceae 43 100% 5
Position on adult host
positionbeetlessites
on flower(s)32
on flowering plant278
on foliage or non-flowering plant143
on plant (unspecified)84
Host plant notes

As with M. rothei, adults are strongly associated with Senna artemisioides and their appearance coincides with the flowering time of these bushes. Recently, however, I encountered it in large numbers on flowering Acacia calamifolia in the southern Flinders Ranges.

¹ LegendregionsSA State Herbarium regions (map)
EA: Eastern, EP: Eyre Peninsula, FR: Flinders Ranges, GT: Gairdner-Torrens, KI: Kangaroo Island, LE: Lake Eyre, MU: Murray, NL: Northern Lofty, NU: Nullarbor, NW: North-Western, SE: South-Eastern, SL: Southern Lofty, YP: Yorke Peninsula
sizeThe ellipse is the correct size when printed, indicative on a desktop screen, and likely to be wrong on a mobile device.