Balacra (Daphaenisca)

Durante, Antonio & Zangrilli, Maria Paola, 2016, Review of subgenus Daphaenisca Kiriakoff, 1953 (Lepidoptera: Erebidae: Arctiinae: Synthomini: Thyretina), with identification keys, and description of three new species, Zootaxa 4117 (2), pp. 151-171 : 153-156

Subgenus Daphaenisca Kiriakoff, 1953

Daphaenisca currently includes the two species daphaena and affinis , very similar in external appearance, and lacking external characters with clear and decisive synapomorphies.

In his catalogue (2009: 34, 35), Przybyłowicz synonymysed the name Balacrella with Daphaenisca, noting that “the differences in genitalia are rather small and do not support the maintenance of two separate subgenera”.

Our re-examination of affinis and daphaena , previously included in Balacrella and Daphaenisca respectively, confirms what was observed by Przybyłowicz (2009).

Firstly, we examined the less stable or more variable characters, such as wing and body colours and patterns, wing venation and spurs formula, which show perfect correspondence between the two species. The second step was to examine the more stable characters, such as male and female genitalia, for which we highlight some differences that justify the species rank, but not their splitting into two subgenera. For instance, the shape of the uncus, considered by Kiriakoff (1957) to be significant in diagnosis, is here seen to be rather variable, and thus not able to support generic or subgeneric diagnosis. This finding is supported by the recent discovery in Gabon of a third species attributable to the subgenus Daphaenisca, of which the uncus has a single point, rather than bifurcate or trifurcate as in daphaena and affinis respectively. The other structures of the male genitalia of the three considered species show a limited degree of interspecific variation, being similar to each other with the same general structure of the valvae and a fairly stout aedeagus.

Regarding wing shape, we noted a clear difference between Daphaenisca and the other close subgenera included in the genus Balacra . To evaluate these differences we performed one-way ANOVA on the forewing length/width ratio, the results consistently reflecting the known taxonomic differences in wing proportions and thereby confirming its stability as differential characters for the Balacra subgenera.

Average forewing ratios are lowest in Lamprobalacra and highest in Daphaenisca (2.09 and 2.62 respectively), which correspond to the largest and smallest widths ( Tab. 1 ). Statistically significant differences in the forewing length/width ratios (p <0.05%) of the selected subgenera are shown ( Tab. 2).

The comparison the other three subgenera proved to be the most significant. Indeed, Daphaenisca has the highest average forewing ratio, corresponding to the smallest widths. The t test values calculated for the other three groups show less marked differences (p-values from 0.19 to 0.08) ( Tab. 3 ). Generally, the statistical analyses were effective in reflecting the known taxonomic similarities between the four subgenera included in the genus Balacra .

Type species. Pseudapiconoma daphaena Hampson, 1898 .

Type locality. R. Niger, Asaba [ Nigeria].

Diagnosis. Smaller than the other subgenera in Balacra (e.g., Pseudapiconoma, Lampobalacra , Balacra ), with more elongated forewings and dark ground colour. Hindwing venation has six veins from the cell (missing Sc+R1 and Rs), whereas in the similar genus Bergeria Kiriakoff, 1952 there are five veins (with M2 also missing).

Description. Adult: subgenus of small-sized species (forewing length 12–19 mm); forewings narrower (length/width ratio 2.5–3) than in other subgenera (i.e., Pseudapiconoma, Lampobalacra , Balacra , length/width ratio 1.5; 2; 2 respectively); hindwings very small, roughly circular or elongated ( Fig. 4 ).

Ground colour dark violaceous to blackish with few yellow and red patches on the wings and body.

Head small with serrate or bipectinate antennae, and short porrect labial palpi.

Forewings homogeneous in colour with very small patches and complete venation (Noctuoidea ground plan); M2 and M3 short-stalked, M1 short-stalked with radius sector Rs4[Rs1(Rs2, Rs3)], and R anastomosing with Sc; areole sometimes present ( Fig. 2 ).

Hindwings with lighter colouration, Thyretini ground plan venation with M2 and M3 stalked and Rs and M1 fused together ( Fig. 3 ).

Legs with spurs formula 0-2-2.

Male genitalia Balacra -like with simple valvae and distal elongation of the valvar costal margin.

Female genitalia with quite long ductus bursae, slightly convoluted and quite rigid. Bursa rather large, ovoidal or spheroidal.

Distribution and ecology. The subgenus is found in equatorial and tropical Africa from Ghana in the West to Uganda in the East. The African Moths website (http://www.africanmoths.com; last visit 5 August 2015) also reports Niger and Angola, but there is no clear reference.

The habitat of the subgenus ranges from deciduous to rain forest.

In Gabon (Ivindo National Park) it flies at least from November to April, throughout the long rainy season, and the short dry and rainy seasons.

Early stages and larval food plants remain unknown for all included species, with the exception of daphaena , whose eggs are herein described for the first time.

Differential characters and possible synapomorphies. The general appearance of the subgenus is better characterised than other Balacra subgenera: the size is quite small; the ground colour is constantly uniform and dark without dots or transparent fenestrae on the forewings; the forewing ratio is constant within the subgenus, and different from other subgenera (see above and Discussion for more details). The latter character is here considered a good synapomorphy at subgeneric level because it seems to be stable within the subgenus Daphaenisca and exclusive to it.

The genitalia show an elongation of the costal valvar margin (a similar elongation in the subgenus Callobalacra Kiriakoff, 1953 does not seem to be of costal origin), and an exclusive connecting structure between the tegumen and uncus which extends inside the tegumen. This structure is considered to be socii (i.e., derived from the caudal margin of the tegumen or even more caudal, but well separated from the uncus). It is regarded as synaphomorphic of the subgenus, since it is not present in the remaining subgenera of the genus Balacra , although there is a superficially similar structure in Callobalacra, where the uncus and tegumen are connected by a clearly sclerotised area, remaining separate however. In the subgenus Heronina Kiriakoff, 1955, the tegumen and uncus are welded together, but in such a different manner that it cannot be seen as homologous to Daphaenisca.

Keys to the species of the subgenus Daphaenisca

Male

1. Male antennae serrate.................................................................................. 2

- Male antennae bipectinate........................................................................ magnoloi

2. Distal end of the uncus trifurcate.................................................................... affinis

- Distal end of the uncus bifurcate.......................................................................... 3

3 Vesica of the aedeagus bearing a single big thorn-like cornutus.......................................... daphaena

- Vesica of the aedeagus bearing a cluster of spine-like cornuti........................................... inexpectata

Female

- corpus bursae smooth without such rows................................................................... 3

3. corpus bursae with single long signum............................................................. inexpectata

- corpus bursae with two long parallel signa........................................................... daphaena

Figures

FIGURES 2 – 4. Morphology. Fig. 2. Forewing venation of Balacra affinis. Fig. 3. Hindwing venation of Balacra magnoloi sp. n. Fig. 4. Forewing sizes and external morphological terms in Daphaenisca subgenus.

Tables

TABLE 1. Mean values (± ES) for each considered subgenus.

Subgenera	Mean forewing ratio	ES
Daphaenisca	2.62	0.17
Pseudapiconoma	2.27	0.25
Lamprobalacra	2.09	0.15
Balacra	2.17	0.08

TABLE 3. Pairwise T-test for all considered subgenera. Values in boldface are statistically significant (p <0.05). Subgenera are listed from top-down in order of similarity level.

Pairwise samples	ρ-value
Daphaenisca vs Balacra	4.86189E- 09
Daphaenisca vs Lamprobalacra	6.24454E- 08
Daphaenisca vs Pseudapiconoma	7.60716E- 05
Pseudapiconoma vs Lamprobalacra	0.019750545
Lamprobalacra vs Balacra	0.040194314
Pseudapiconoma vs Balacra	0.086862363