Oosagitta gen. nov. from tropical Africa, with revision of two species and description of four new species (Coleoptera: Chrysomelidae, Galerucinae)

After our taxonomic revision of Ootheca Chevrolat, 1837, and the description of Oothecoides Kortenhaus & Wagner, 2011 and Ootibia Kortenhaus & Wagner, 2012, it became clear that a further four galerucine species, closely related to the above named taxa, form a distinct monophyletic group, that constitutes a new genus, Oosagitta gen. nov. with O. anningae sp. nov., O. geescheae sp. nov., O. melanopicta sp. nov. and O. thomasi sp. nov.. Exosoma angolensis Laboissière, 1939, the type species of the new genus, and Ergana minuta Laboissière, 1937 are newly transferred to Oosagitta gen. nov. All species of Oosagitta gen. nov. are characterized by a broad body and pronotum, a more or less convex dorsum and short legs, and as such are most similar to the other above named genera. The antennae of Oosagitta gen. nov. are distinctly longer than those of Ootheca, Oothecoides and Ootibia. Genital structures of the males allow a reliable identification of the genus. (Re-)descriptions are given for all species, including semi-schematic illustrations depicting the habitus outline, shape of the basal antennomeres and the median lobe. Photographs of the name-bearing types and distribution maps are provided.


Introduction
Over the last years we revised a number of species, originally described in the galerucine genus Ootheca Chevrolat, 1837 (Kortenhaus & Wagner 2010) or its junior synonym Ergana Chapuis, 1879 and species later transferred from Malacosoma Chevrolat, 1837 -and its replacement name Exosoma Jacoby, 1906 -to Ootheca.We identified several species, which have to be excluded from Ootheca (Kortenhaus & Wagner 2011, 2012).Some of them, characterized by asymmetrical structures of the median lobe and a comparatively dorsoventrally compressed body shape, have been transferred to Oothecoides Kortenhaus & Wagner, 2011.Further two species, with sexual dimorphic characters of the metatibia and a distinct male genital pattern, have been transferred to and recently described in Ootibia Kortenhaus & Wagner, 2012.Two other species, Exosoma angolensis Laboissière, 1939 andErgana minuta Laboissière, 1937, do not belong to these taxa and have to be transferred, together with four newly described species, to a new genus that is herein described.Oosagitta gen.nov.has the broad pronotum, more or less convex dorsum, short legs and also the shape of the spermatheca in common with Ootheca, Oothecoides and Ootibia, but its antennomeres are significantly more elongated.The most distinctive character for this new group is the male genitalia, that possesses a peculiar arrow-like apical part of the endophallus, a very long median tectum and a pair of very long, elongated tectorial spures that can be considered as a synapomorphic character.

Abbreviations
Our revision is based on 1433 specimens from the following collections (Tab.O. minuta (Laboissière, 1937)   Relative measurements were: PW/PL = pronotal width to pronotal length EW/EL = maximum width of both elytra combined to elytral length 2./3.= length of second to third antennomere 3./4.= length of third to fourth antennomere WE/DE = maximum width of eye to minimum distance between eyes TA/TI = length of basimetatarsus to length of metatibia (Fig. 1) For each species, a standard set of figures is given.External characters are documented by dorsal semi-schematic habitus illustrations, including the left antenna, detailed illustrations of the four basal antennomeres of males and females, and legs on the right-hand side of the body.In one case, the illustration depicts the elytral colour pattern.The male genitalic structures are illustrated in dorsal and lateral views.Variation in spermatecal shape is very small between species and therefore only given in the description of the genus.General structures of the head, ventral side of the thorax and metathoracic wing are very similar to those of Ootheca, and details can be found in our revision of that genus (Kortenhaus & Wagner 2010).For name-bearing type specimens, the label data are cited verbatim and sexes are given; data for all other specimens have been standardized and include the following information: country, province, numbers of specimens, locality, latitude and longitude coordinates, altitude, date, collector and depositary (in brackets).Localities are given as precisely as possible.Countries and localities (e.g.towns), recorded as traditional names on labels, are listed, together with their current names; coordinates were taken from the geographical database GeoNames; if a location remains unidentified, mean coordinates of the given district or region were used; in cases of doubt, where there was one location with many coordinate possibilities, we did not allocate coordinates.Data were imported into the program ArcGis (ESRI-Arc-Map Version 9.3) to produce GIS-based distribution maps.
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.3.10-6.20mm; 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.
abdomen.Brown.male geniTalia.Median lobe slightly waisted in dorsal view (Fig. 7A), conical and incised at apex.Tectum is conical with a very elongated, slender apical part that is bent ventrally at the apex.It has long, slender tectorial spures at each side (Fig. 7A, C).Endophallus brush emerges from broad, arrow-like structure (Fig. 7B).Orifice of median lobe is ovoid with a rather deep incision (Fig. 7A).

Distribution
Widely distributed in Central, East and Southern Africa, from the Congo Basin towards Kenya in the northeast and to Zambia and northern Namibia in the South (Fig. 8).

Differential diagnosis
Oosagitta minuta comb.nov. is the smallest species of the genus with a total body length between 3.10 and 4.20 mm.There is no other specimen of the other five species of such small size known.Antennae of O. minuta comb.nov.are shorter than those of the other described species: mean antennal length to total body length is 0.56-0.65 (other species 0.75-1.00).Also the coloration differs strongly from the other species, since O. minuta comb.nov.has dark brown elytron, while all other species show yellowish to yellowish-brown elytron throughout or yellow with brownish base and apex (O.geescheae sp.nov.).
Thorax.Pronotum yellowish with very delicate punctation.Pronotal width 1.50-1.90mm (mean 1.71 mm), length of pronotum 0.90-1.20 mm (mean 1.05 mm), pronotal width to length 1.50-1.73(mean 1.62).Elytron is yellowish and has irregular punctation, only a bit coarser than pronotum.Elytral length 3.35-4.25mm (mean 3.91 mm), maximum width of both elytra combined 2.50-3.45mm (mean 3.04 mm), ratio of maximum width of elytra combined to length of elytron 0.73-0.83(mean 0.78).Pro-, meso-and metathorax, abdomen and legs are yellowish.Tibia is gently curved.Length of basimetatarsus to length of metatibia 0.24-0.32(mean 0.29).male geniTalia.Aedeagus very broad, rather erect, only the outermost apex of median lobe and tectum curved ventrally (Fig. 17C).The slightly waisted, broad tectum covers basal two thirds of very long, slightly bent and apically crossed tectorial spures that are much longer than the ventral part of the median lobe (Fig. 17A).Endophallus long, with slender base, two short "arrow-hooks" and very slender and long apical part that is emerging out of the median lobe (Fig. 17A, B).Orifice of median lobe ovoid with a rather deep incision (Fig. 17A).

Distribution
Western Africa from Ivory Coast towards Togo (Fig. 13).

Differential diagnosis
Oosagitta melanoptica sp.nov.has a peculiar character in the significant black patch behind the eye.Further differentiation is possible by the characteristic broad shape of the median lobe.

Discussion
During our revision of Ootheca, a group of galerucines endemic to tropical Africa, it became quickly clear that according to the generotype Ootheca mutabilis Sahlberg, 1823, only a "core" group will be remain in that genus.There was obviously no clear generic concept of Ootheca in the nineteenth century, as for many other insect genera, and several leaf beetle species, having a "compact" body shape with broad pronotum, strongly bulged dorsum and short antennae and legs are described in combination with Ootheca.Weise gave a first revision of Ootheca, in which he critically revised the characters of O. mutabilis, that he attributed to Chapuis, 1879, and described three new species from German East Africa (Tanzania).He corrected some misinterpretations, e.g.concerning the prothoracic coxal cavities that Chapuis (1879) described as "ouvertes", but he found as completely closed, what now could be confirmed.Weise also referred to the problems the generic delimitation of Ootheca cause and to the complexity to distinguish the species, but found good evidence for species identification in the male genitalia.This underlines the high quality of his work, since more than one hundred years ago, dissection of genitalia was an unusual method to delimitate insect species.In our recent revision, the male genital characters are most crucial for the identification of single species, and also for the delimitation of Ootheca as compared to other galerucine groups taking phylogenetic principles into account.Several characters of the median lobe and endophallic armature can be interpreted as apomorphic characters.After the recent description of Oothecoides and Ootibia, we herein split the third group from Ootheca, where in total six species are characterized by a distinct endophallic pattern that does not, to our knowledge, occur in any other group of Afrotropical galerucines.There are some more species originally described in Ootheca, Ergana, and some further described in Exosoma that are most likely closely related to the genera named above, but not yet revised.Some work is left for the future.

Table 1 .
Numbers of examined specimens in the studied collections.Depending on the available specimens, 11 to 30 specimens were measured per species.Absolute a dark brown elytron, legs and underside and is much smaller.Oosagitta angolensis comb.nov. is on average the largest species of the group, and, in the majority of cases, can be easily differentiated from other species by size.Total body length varies between 4.90 and 6.20 mm (O.geescheae sp.nov.4.50-4.80mm,O.anningae sp.nov.4.25-5.35mm,O. minuta comb.nov.3.10-4.20mm,O. thomasi  sp.nov.4.65-5.50mm,O. melanoptica sp.nov.4.15-4.70mm).The shape of the median lobe with slender, incised apex, long tectum with very slender tectorial spures allows a clear identification of the males.