Bracalba Dodd

Burks, Roger A., Masner, Lubomir, Johnson, Norman F. & Austin, Andrew D., 2012, Taxonomic revision of Bracalba Dodd (Hymenoptera, Platygastridae s. l.), a parasitoid wasp genus endemic to Australia, ZooKeys 236, pp. 1-53 : 3-6

Bracalba Dodd

Bracalba Dodd 1931: 78 (original description. Type: Bracalba laminata Dodd, by original designation); Muesebeck and Walkley 1956: 336 (citation of type species); Masner 1976: 22, 23 (description, key to separate Baryconus Förster, Bracalba Dodd, Chromoteleia Ashmead, Oxyscelio Kieffer); Galloway and Austin 1984: 8, 13 (diagnosis, list of species described from Australia, keyed); Johnson 1992: 354 (catalog of world species); Austin and Field 1997: 18, 68 (structure of ovipositor system, discussion of phylogenetic relationships, genus misplaced in Baryconini ).

Diagnosis.

Eye setose; frontal depression present; antenna 12-segmented; netrion present; postmarginal vein of fore wing present, longer than marginal and stigmal veins; mesotibia and metatibia each with 1 spur; metascutellum setose dorsally and ventrally; ovipositor Scelio -type.

Description.

Body length: 2.75-6.88 mm (n=78).

Head. Head shape in dorsal view: transverse. Hyperoccipital carina: absent. Occipital carina: present laterally, broadly interrupted medially; present, complete medially. Occipital carina sculpture: crenulate. OOL: lateral ocellus nearly contiguous with inner orbits, OOL < 0.5 OD. Upper frons: convex, without frontal shelf. Scrobe shape: frons with shallow unmargined depression above antennal foramina. Frons sculpture: areolate rugose, transversely striate within scrobe; areolate rugose, scrobe sparsely punctate. Submedian carina: absent. Orbital carina: absent. Inner orbits: diverging ventrally. IOS/EH: IOS slightly less than EH. Interantennal process: triangular in lateral view, well-developed. Central keel: absent. Antennal foramen opening: nearly anteriorly. Lower frons striae: absent. Malar sulcus: present. Compound eye size: of normal proportions, not significantly reduced. Compound eye setation: densely setose; sparsely setose. Gena: narrow, weakly convex, receding behind posterior orbit. Clypeus shape: transversely rectangular. Apical margin of clypeus: rounded; with a small median point. Anteclypeus: absent. Postclypeus: absent. Labrum: not visible. Mandible shape: moderate. Mandibular teeth: apex with 2, acute, subequal teeth; apex tridentate, teeth acute, middle tooth distinctly shortest. Arrangement of mandibular teeth: transverse. Number of maxillary palpomeres: 4. Shape of maxillary palpomeres: cylindrical. Number of labial palpomeres: 2.

Antenna. Number of antennomeres in female: 12. Number of antennomeres in male: 12. Insertion of radicle into A1: parallel to longitudinal axis of A1. Shape of A1: more or less cylindrical, not flattened. Length of A3 of female: distinctly longer than A2. Number of clavomeres in female antenna: 8. Claval formula of female antenna: A12-A7/1-2-2-2-2-2; A12-A6/1-2-2-2-2-2-2; A12-A6/1-2-2-2-2-2-1. Arrangement of doubled multiporous plate sensilla on female clava: in longitudinal pairs. Tyloid distribution on male antenna: A5 only. Shape of male flagellum: filiform.

Mesosoma. Mesosoma shape in dorsal view: longer than wide. Mesosoma shape in lateral view: longer than high. Medial portion of transverse pronotal carina: absent. Posterior apex of pronotum in dorsal view: straight, bifid apically to articulate with tegula. Vertical epomial carina: absent. Dorsal epomial carina (lateral portion of transverse pronotal carina of Vilhelmsen et al. (2010)): absent. Central pronotal area: vertical, not visible in dorsal view. Lateral face of pronotum: weakly concave below position of dorsal epomial carina. Netrion: present. Netrion shape: moderately wide, closed ventrally. Anterior portion of mesoscutum: vertical, flexed ventrally to meet pronotum. Mesoscutum shape: pentagonal in outline, posterolateral corner rounded. Skaphion: absent. Notauli: present, percurrent. Parapsidal lines: absent. Admedial lines: absent. Transscutal articulation: well-developed, crenulate. Shape of mesoscutellum: quadrate to trapezoidal. Armature of mesoscutellum: absent. Surface of mesoscutellum: convex throughout. Median longitudinal furrow on mesoscutellum: absent; present. Shape of axillula: small, dorsal margin sinuate. Metascutellum in dorsal view: clearly differentiated. Metascutellar armature: produced into flattened plate. Metascutellar setation: setose dorsally and ventrally. Metapostnotum: not defined externally. Extent of metasomal depression of propodeum: percurrent, extending anteriorly to anterior margin of propodeum. Lateral propodeal projection: well-developed, extending clearly beyond anterior margin of T1. Mesopleural carina: absent or strongly abbreviated, present only near mid coxa. Mesal course of acetabular carina: projecting anteriorly, but too short to intercede between fore coxae. Mesopleural pit: absent. Sternaulus: absent. Posterodorsal corner of mesopleuron: rounded anteriorly.

Legs. Number of mid tibial spurs: 1. Number of hind tibial spurs: 1. Dorsal surface of hind coxa: smooth. Hind tibia shape: cylindrical, ecarinate. Trochantellus: indicated by transverse sulcus on femur.

Wings. Wing development of female: macropterous. Wing development of male: macropterous. Tubular veins in fore wing: present. Bulla of fore wing R: absent. Extent of marginal venation of fore wing: distinct marginal or postmarginal veins developed. Origin of r-rs in fore wing: arising at junction of R/R1 with costal margin. Development of basal vein (Rs+M) in fore wing: nebulous, weakly pigmented. Development of R in hind wing: elongate, extending to costal margin.

Metasoma. Number of external terga in female: 6. Number of external sterna in female: 6. Number of external terga in male: 8. Number of external sterna in male: 7. Shape of metasoma: acuminate, widest submedially. Laterotergites: present, narrow. Laterosternites: present. T1 of female: raised medially into low, rectangular or subelliptical platform, laterally depressed. Relative size of metasomal terga: T2-T4 largest, subequal in size. Terga with basal crenulae: T1-T4. Sublateral carinae on terga: absent. Median longitudinal carina on metasomal terga: absent; present. Distribution of felt fields: absent. Ovipositor type: Scelio-type ( Austin and Field 1997).

Etymology.

Dodd did not specify the source of the name for this genus, but presumably it is derived the name of the Queensland town of Bracalba. (Dodd also used the names of Merriwa, NSW and Nyleta, QLD for other genera.) He originally combined this name with two species epithets of variable gender, both coined in feminine form: Bracalba cuneata and Bracalba laminata , clearly indicating that he intended Bracalba to be a feminine noun.

Distribution.

Bracalba has been collected only from Australia (Fig. 1), and has seldom been collected north of the Tropic of Capricorn. The furthest north that any Bracalba has been collected was at 24°39'S, and only two species have been found north of Alice Springs, NT. Location records show that the highest species diversity occurs in the Pilbara and south-western regions of Western Australia.

Biology.

The hosts of Bracalba are unknown but the structure of the ovipositor ( Scelio -type; Austin and Field 1997) and specimens reared from eggs confirm that the genus is associated with orthopteran hosts. These eggs could not be identified beyond the ordinal level.

Relationships among species.

The implicit enumeration search found two optimum trees of 166 steps (strict consensus: Fig. 2). Bracalba was monophyletic with respect to the Chromoteleia outgroup (bootstrap = 100). Intuitively-based species groups were not monophyletic in the analysis, but this was likely due to homoplasy resulting from inclusion of many sculptural and coloration characters that have mainly descriptive value. Species with a bend at metasomal segment 4 in females did not form a monophyletic group, but this was complicated by the smooth transition in this character from being distinctively present to clearly absent. One feature that was helpful in determining species group, but which was not reported in the key because it was too difficult to accurately and consistently assess, was the lateral margin of the dorsal axillar area. In the cuneata-group, the dorsal axillar area was essentially triangular, broadening posteriorly, with the lateral margin sometimes forming a posterior tooth. In the laminata-group the dorsal axillar area was generally more nearly semicircular, broadest at midlength, and with the lateral margin not forming a posterior tooth. Apparent variation, and difficultly in observing this character with confidence, caused us to omit it from the key.

Key to species of Bracalba

Note: It is imperative to consult figures when using the below key, as shape features of the metascutellum and metasoma are very important in identifying Bracalba species with any hope of accuracy.