Oosagitta, Kortenhaus & Wagner, 2013

Kortenhaus, Sabine & Wagner, Thomas, 2013, Oosagitta gen. nov. from tropical Africa, with revision of two species and description of four new species (Coleoptera: Chrysomelidae, Galerucinae), European Journal of Taxonomy 58, pp. 1-24 : 4-6

Oosagitta gen. nov.

urn:lsid:zoobank.org:act:11FBE0A7-E2BB-4072-B6BD-87B5AEBBA47E

Type species

Exosoma angolensis Laboissière, 1939 .

Differential diagnosis

Oosagitta gen. nov. are Galerucinae with an elongate-ovate body shape, elytron slightly widened in the posterior half, convexly rounded, and a pronotum slightly narrower than the elytra ( Figs 2 , 10 , 15 , 19 , 23 , 27 ). Head broad, with widely separated, strongly protruding eyes ( Fig. 1 ). Legs short and robust, the basi-tarsomeres are slightly enlarged and the claws appendiculate ( Fig. 4 ).

From Ootibia it can be differentiated by the characteristic shaped metatibia of the male specimens. From this genus, as from Ootheca and Oothecoides , it can be differentiated by the long and slender antennomeres. The mean antennal length to total body length ratio of Oosagitta gen. nov. is 0.60–0.93, with an overlap ratio to the other three genera of 0.60 in O. minuta comb. nov. Thus Oosagitta gen. nov. can be differentiated from Ootheca (mean antennal length to total body length ratio 0.47–0.61), from most specimens of Oothecoides (0.61–0.72) and from Ootibia (0.66–0.71). Length of the second antennomere is about 60 % of the third and length of the third antennomere about 70 % of the fourth ( Figs 5 , 11 , 16 , 20 , 24 , 28 ). With respect to the maximum height in lateral view, Oosagitta gen. nov. ( Fig. 3 ) is similarly dorso-ventrally compressed as Oothecoides , while Ootheca and Ootibia are more bulged. Due to significant overlap in body size, measurements and colouration at least of some species, a reliable identification of these four genera is doubtless possible by dissection of the male genitalia.

The symmetric median lobe of Oosagitta gen. nov. is poorly conical towards apex, slightly down-curved in lateral view, tapering to two more or less elongated tectorial spures separated by an incision and has dilated basal orifice. The tectum possesses a broad base and a narrow apex. The endophallus shows two triangular appendices at its apex ( Figs 7A , 12A , 17A , 21A , 25A , 29A ), the endophallus brush emerges from this arrow-like structure ( Figs 7B , 12B , 17B , 21A , 25B , 29A ). This endophallus-“armature” of Oosagitta gen. nov. allows a clear differentiation from the shape of the endophallus of Ootheca . The similarity between aedeagal structures of Oosagitta gen. nov. and those of Ootheca is obvious: the symmetrical median lobe of Ootheca is usually parallel-sided, slightly conical towards the apex, or constricted in the middle. The apex can be either rounded or pointed without an apical incision, or have a deeply U-shaped apical incision. In lateral view, the median lobe is more or less evenly downcurved. The tectum is very characteristic in Ootheca , consisting of two dorsal, more or less slender, often apically hooked, tectorial spurs that are attached at the base of the apical third of the median lobe, and extend from its middle sometimes to near its apex. However no long median tectum occurs in Ootheca . The apical part of the symmetrical endophallus can usually be distinguished clearly between the bases of the tectorial spurs.

The main difference between Oosagitta gen. nov. and Oothecoides concerns the endophallus: only Oosagitta gen. nov. possesses a symmetrical triangular, arrow-like apex of the endophallus, Oothecoides has two very specific asymmetrical spines. The aedeagal shape of Oosagitta gen. nov. differs strongly from that of Ootibia. The shape of the median lobe in Ootibia (obtuse, compact, almost rectangular, parallel-sided, slightly conical towards apex, slightly down-curved in lateral view, with a very dilated basal orifice) is also different. Apically, the median lobe of Ootibia displays two ventrally situated projections, like “ears” (in dorsal view), which taper to form one or two points (in lateral view). The endophallus has a peculiar endophallic brush and two symmetrical triangular appendices.

Etymology

Combination of Ootheca and sagitta, which refers to the arrow-like shape of the endophallus; gender: female.

Description

TOTAL LENGTH. 3.10–6.20 mm; means of total body length for the species range from 3.75 to 5.54 mm. Females are somewhat longer than males.

HEAD. Yellowish to dark brown, labrum in the same colour as head, only in O. geescheae sp. nov., the yellowish head becomes darker towards labrum. Rarely ( O. melanopicta sp. nov.) with dark brown to black patch behind the eye. Maxillary palps yellowish to brown, last palpomere conical with fine apex. Eyes convex and ovate, separated by triangular frontal calli, and a transverse, curved depression divides the frons from the vertex ( Fig. 1 ); ratio for maximum eye width to minimum distance between eyes varies from 0.55–0.92 (means of species vary between 0.67 and 0.83). Antennae completely yellowish ( O. anningae sp. nov., O. melanopicta sp. nov.), brown ( O. angolensis comb. nov.), yellowish and the apical antennomere with darker apex ( O. geescheae sp. nov.), basal first antennal article yellowish, antennomeres 2–11 brown ( O. thomasi sp. nov.) or basal four antennomeres yellowish, antennae becoming darker towards apex ( O. minuta comb. nov.). Mean antennal length ratio to total body length ratio 0.60–0.93; mean length ratio of antennomere two to three 0.43–0.64; mean length ratio of antennomere three to four 0.69–0.83.

THORAX. Pronotum convexly rounded dorsally, lateral margins clearly differentiated from disc, anterior angles rounded ( Fig. 1 ), disc convexly rounded; finely punctate, unicolourous yellowish or brown; pronotal length 0.65–1.30 mm (means of species vary between 0.81 and 1.17 mm); pronotal width 1.00–2.00 mm (means of species vary between 1.28 and 1.85 mm); pronotal width to length ratio 1.41– 1.94 mm (means of species vary between 1.56 and 1.76 mm). Prothorax dark brown to yellowish. Elytron unicolourous or with a brown base and apex of elytron in only one species ( O. geescheae sp. nov.); elytron coarsely and more deeply punctate than pronotum; punctation irregular; length of elytron 2.35–4.95 mm (means of species vary between 2.82 and 4.33 mm); maximum width of elytra combined 1.80–3.70 mm (means of species vary between 2.23 and 3.31 mm); maximum width of elytra combined to length of elytron ratio 0.66–0.88 (means of species vary between 0.72 and 0.88). Scutellum almost triangular, dark brown/black or yellowish. Meso- and metathorax in same colour. Legs unicolourous yellowish to brown or dark brown with paler brown coxae and distal/proximal parts of femur and tibia ( O. minuta comb. nov.). Mean length of metatarsus to length of metatibia 0.24–0.35 (means of species vary between 0.29 and 0.32).

ABDOMINAL VENTRITES. Five visible ventrites (seven sternites; Fig. 3 ) of the same colour as the pro-/ meso- and metathorax. Apical sternite in females evenly rounded, males with two incisions in outer apical margin.

MALE GENITALIA. Median lobe, tectum and endophallus symmetrical ( Figs 7 , 12 , 17 , 21 , 25 , 29 ). Median lobe slightly waisted in the middle and conical towards apex, where it is pointed ( Figs 12A , 29A ) or shallowly incised ( Figs 7A , 17A , 21A , 25A ). In lateral view, median lobe is more or less curved ventrally ( Figs 7C , 12C , 21C , 25B , 29B ), sometimes with significant hook ( Fig. 17C ). The tectum with broad base and strongly narrowed to apex, long as the ventral part of the median lobe ( Figs 7A , 17A , 21A , 25A , 29A ) or shorter ( Fig. 12A ), covering most parts of the endophallus by forming a tapering tip ( Figs 7 , 25 29 ), a slender, rectangular structure ( Fig. 21 ) or a shorter, conical apex ( Figs 12 , 17 ). The median part of the tectum has moveable, slender tectorial spures on each side that are straight at apex ( Figs 7 , 21 , 25 , 29 ), hooked ( Fig. 12 ) or crossed ( Fig. 17 , 29 ). The endophallus possesses two triangular appendices at its apex, giving it an arrow-like appearance ( Figs 7B , 12B , 17B , 21A , 25A , 29A ). The basal aedeagal orifice is very dilated with an incision ( Figs 7A , 12A , 17A , 21A , 25A , 29A ).

FEMALE GENITALIA. Spermatheca with spherical nodulus. Spermathecal ductus slightly sunken in the nodulus, cornu slender, strongly and evenly curved ( Fig. 6 ).

Host plants, biology and immature stages

Unknown.

Figures

Figs 2-4. Oosagitta angolensis comb. nov. 2. Habitus, semi-schematic dorsal view, ♀. 3. Habitus, lateral view, ♀. 4. Legs: A. Prothoracic leg. B. Mesothoracic leg. C. Metathoracic leg. Scale bars = 1 mm.

Figs 10-12. Oosagitta minuta comb. nov. 10. Habitus, semi-schematic dorsal view. 11. Basal four antennomeres of 2 ♂♂ and 2 ♀♀. 12. Median lobe: A. Dorsal. B. Detail: apex of endophallus. C. Lateral. Scale bars = 1 mm.

Figs 15-17. O. anningae sp. nov. 15. Habitus, semi-schematic dorsal view. 16. Basal four antennomeres of 2 ♂♂ and 2 ♀♀. 17. Median lobe. A. Dorsal. B. Detail: apex of endophallus. C. Lateral. Scale bars: 1 mm.

Figs 19-21. Oosagitta geescheae sp. nov. 19. Habitus, semi-schematic dorsal view. 20. Basal four antennomeres of 2 ♂♂ and 2 ♀♀. 21. Median lobe. A. Dorsal. B. Lateral. Scale bars: 1 mm.

Figs 23-25. Oosagitta thomasi sp. nov. 23. Habitus, semi-schematic dorsal view. 24. Basal four antennomeres of 2 ♂♂ and 2 ♀♀. 25. Median lobe. A. Dorsal. B. Lateral. Scale bars: 1 mm.

Figs 27-29. Oosagitta melanopicta sp. nov. 27. Habitus, semi-schematic dorsal view. 28. Basal four antennomeres of 2 ♂♂ and 2 ♀♀. 29. Median lobe. A. Dorsal. B. Lateral. Scale bars: 1 mm.

Fig. 1. Measurements taken. Absolute measurements: TL = total length from apex of labrum to apex of elytron; PL = pronotal length; PW = maximum pronotal width; EL = elytral length; EW = maximum width of elytra combined. Relative measurements: 2, 3, 4 = length of second, third and fourth antennomeres; DE = minimum distance between eyes; WE = maximum width of eye; TA = length of basimetatarsus; TI = length of metatibia.

Figs 5-7. Oosagitta angolensis comb. nov. 5. Basal four antennomeres of 2 ♂♂ and 2 ♀♀. 6. Spermathecae of 3 ♀♀. 7. Median lobe: A. Dorsal. B. Detail: apex of endophallus. C. Lateral. Scale bars = 1 mm.