Boletín de Entomología Venezolana (NS). 1983-1984, Vol 3(1-3):21-28
Oxyagrion fluviatile sp. n. from Venezuela, with notes on Oxyagrion cardinale Fraser (Odonata: Coenagrionidae)

Resumen

Se dan una descripción y figuras de Oxyagrion fluviatile sp. n. (holotipo: Venezuela, Miranda, Guatopo). Esta especie parece íntimamente relacionada con O. cardinale Fraser que es ilustrada aquí por la primera vez. Los géneros Oxyagrion y Acanthagrion, ambos Selys, 1876, son comparados y las características que los separan son cuestionadas.

Abstract

A description and figures of Oxyagrion fluviatile sp. n. (holotype: Venezuela, Miranda, Guatopo) are given. This species is probably a close relative of O. cardinale Fraser which is figured here for the first time. Some general remarks on the affinities of and the differences between Acanthagrion and Oxyagrion, both Selys, 1876, are also presented.

Introduction

Most of the specimens which served for the description of this new species were set apart many years ago by the late Prof. Dr. J. Racenis, who thought they may represent not only a new species, but a new genus as well. However, he never published any description or diagnosis. In his "Preliminary List of Venezuelan Odonata" (RACENIS, 1966) he mentions the species as "Acanthabasis fluviatilis" gen. n. sp n.. A recent careful reexamination of the specimens brought me to the conclusion that the species may be identical with the Peruvian Oxyagrion cardinals, described by FRASER (1946) on the base of a single female. Fortunately, Prof. Dr. E. Osuna, from our Institute, is doing some research work at the British Museum (Natural History), where Fraser's type specimen is kept, and was so kind to provide me with additional data, photographs, and some drawings of the holotype cardinale. It then became evident, that fluviatile sp. n. can not be nonspecific with that species Some comparative remarks, as well as the reasons for assigning fluviatile sp. n. to the genus Oxyagrion are presented below.

Oxyagrion fluviatile sp. n.
(Figs. 1-9)

Description of the male (holotype):

Labium creamy yellow, labrum and clypeus grey (blue in life), a brown median spot at the base of labrum. Frons rounded; the two basal segments of antennae pale brown; apex of second segment and remaining segments, black. Vertex pale blue, a fine black line dividing it from occiput. Postocular spots not neatly delimitated, sky blue and spotted with approximately ten dark brown points each, most of these points bearing a single hair. Top of head otherwise rusty, but possibly partly marked with blue in life Head pale beneath. Prothorax dorsally pale blue a brown dash on each side on the median lobe; posterior lobe laterally straight, smoothly rounded in the middle' and with a small central notch. Posterior margin of the mesostigmal laminae sharply erect and forming a ridge. Furrow behind mesostigmal laminae blackish. Dorsum of pterothorax with a rusty median stripe and pale blue antehumeral stripes The latter are enlarged basally and apically, but narrower than the former, in the middle. Humeral stripes rusty, confluent with the golden brown mesokatepisterna. Distally, they are separated from the alar ridge by a dark brown spot on the mesopleural suture. A similar spot occupies the upper end of the metapleural suture. The larger part of the mesepimeron, not covered by the rusty colour of the humeral stripe, is blue, as well as the metepisternum The metepimeron and the ventral parts of thorax are creamy white. There is a linear black spot on the lower posterior angle of metepimeron, and a similar spot just below the root of each wing, on the antealar ridge. Abdominal segment I dorsally blue with a brown twin-spot at the base. Segment 2 similar but with a brown rhomboidal transverse spot at three fourths the segment's length. Segment 3 also blue dorsally but with a narrow brown median line and a big brown subapical spot. On segments 4, ~ and 6, this spot assumes the form of a broad apical transverse band. The base in these segments is blue, the central (dorsal) parts however, are mixed with rust red. Dorsum of segment 7 dark brown to black, with a blue apex beyond the black subapical spinules. Segments 8, 9 and 10 are blue above the latter with an incomplete dark basal line Segment 10 is higher than 9, its apical margin with a very weak incision. Anal appendages slightly shorter than the last segment, the superiors slanting and with the inner surface pale coloured, the outer surface dark brown ;the dividing line between these two colours marked by a groove. At their upper angle, the superiors are provided with an acute, mesally directed tooth and at mid-height with a pencil of yellow hairs. The inferiors are creamy white and as long as the superiors, the brown apices slightly curved in and upwards. A perfect figure of the deeply bilobate penis can be appreciated in LEONARD (1977 plate V, fig. A1A2), drawn after a male from Aracataca, Magdalena, Colombia, although labelled erroneously "Aeolagrion sp.". The legs are creamy coloured, but with the apices of femora and tibiae, and the spines, brown.

The tibial spines are shorter than the spaces between them. The tarsi, including the claws, are predominantly brown. The teeth of the tarsal claws are very short, and at roughly four fifths the length of the claws. The wings are petiolated until Ac or very slightly beyond; arculus at second antenodal.

The pterostigma is oblique, lozenge-shaped, in hind wing shorter than in front wing, and of yellow colour, but darker in center. Venation rusty. Total length 35 mm ;abdomen (incl. app ) 29,3 mm ;hind wing 18,5 mm.

The colour pattern of the 12 paratype males is, as far as preserved, similar to that of the holotype. Total length 34,5 - 36 mm; abdomen 27,5 - 30 mm ;hind wing 18 - 19 mm.

Description of the female

Colour pattern almost the same as in the male, but the basal half of segment 8 seems to be brown instead of blue. The hind margin of the prothorax is almost straight, with a small central notch, the posterior border of the mesostigmal laminae is not as much raised as in the male. There are no mesepisternal fossae. However, in two of the six females examined a minute hole is present at each side of the median carina right behind its anterior bifurcation. This hole is doubtless a wound inflicted to the cuticula by the grasping of the sharp teeth on the upper angle of the male superior appendages, during copula. It is noteworthy that in one male (Nr. 4219) these punctures have also been observed, a fact which suggests that this male has erroneously been taken into tandem by another male. A strong ventral spine is present on segment 8. The ovipositor reaches to almost the posterior margin of segment 10

Total length 32-35 mm abdomen 26-28,5 mm .hind wing 18-20 mm.

General venational features of O. fluviatile sp. n. (H = holotype): Postnodals in front wings 9 pn in both wings: 1 ♂, 1 ♀(11 %); in one wing 9 in the other 10 pn: 7 ♂♂, 2 ♀♀; (47 %); 10 pn in both wings: 4 ♂♂(H), 3 ♀♀(37 %); in one wing 10, in the other 11 pn 1 ♂(5 %). Postnodals in hind wings: 8 pn in both wings l l ♂♂(H), 4 ♀♀(78%); in one wing 8, in the other 9 pn 1♂, 1 ♀(11%); 9 pn in both wings 1♂,1♀(11%). Origin of R3 in front wings: at fourth pn in one wing, -at or near- fifth in the other: 2 ♂♂, 1 Image removed.(16 %); at or close to the fifth pn in both wings: 11Image removed.Image removed.(H), 5 ♀♀(84%). Origin of R3 in hind wings. at fourth pn in both wings: 12 ♂♂(H), 6 ♀♀(95 %); between fourth and fifth pn in one wing of l ♂ (5%). Origin of IR2 in front wings: at seventh pn in both wings: 1 ♂, 1 Image removed. (11%); in one wing at seventh, in the other at eighth pn 2 ♀♀ (11%) at eighth pn in both wings 12 ♂♂ (H); 3 ♀♀ (78%). Origin of IR2 in hind wings: at seventh pn in both wings: 8 ♂♂ (H), 5 ♀♀(68%); in one wing at seventh, in the other at eighth pn 5 ♂♂, 1 ♀ (32%). One male with damaged wings, is not included in the above list.

Material examined: 1 ♂ holotype, 13 ♂♂ and 6 ♀♀ paratypes. All specimens are deposited at the Instituto de Zoología Agrícola, Facultad de Agronomia, Universidad Central de Venezuela, Maracay, VENEZUELA: Guatopo, Miranda, 1 ♂ (holotype, Nr. 9076), 1.XI.1954, El Limón, Aragua, 1 ♂ (9074), 30.III.1955, both J. Racenis leg.; 1 ♂ (14384), 9.IX. 1979 F. Fernández Y. leg ;San Silvestre, Barinas, 1 ♂ (4220), 20.XII.1957; 1 ♀ (4221), 1 ♀ (4234), 21.XII.1957; 2 ♂♂(4217, 4219), 22.XII.1957; 2 ♀♀ (4218, 4222), 23.XII.1957, all J. Racenis leg.; Ticoporo, Barinas, 1 ♀ (14385), 3-10.IV.1966, F. Fernández Y. & L. J. Joly leg.; 1 ♂ (13040), 31.III.1969, J. Racenis leg. ;Bejuma, Carabobo, 1 ♂(12855), 14.II.1920, Williamson & Ditzler leg; Calabozo, Guárico, 1 ♀ (14386), 20.IV.l979, M. Cermeli leg.; Espino, Guárico, 1 ♂ (9072), 21.XII.1954; 1 ♂ (9077), 28.XII.1954; 1 ♂ (9073), 2.I.1955; La Peña Guárico 1 ♂ (9075), l9.III.1956; Pericoco, Guárico, 1 ♀ (10766), 3,VIII.1955, all J. Racenis leg.; San Cristóbal, Táchira, 1 ♂ (14387), 17 II.1981, Correa leg

Comparison of female O. fluviatile sp. n with the holotype female of O. cardinale Fraser

Both species do not differ much in colouration. In fluviatile sp. n., however, dark points are present on the occiput, but absent in cardinale. The total length of fluviatile sp. n. varies between 32 and 35 mm (abdomen 26-28,5), while cardinale is 40 mm long (abdomen 33). No specimen of fluviatile sp. n. has more than 11 postnodals in fore wings and 9 in hind wings; cardinale has 13 and 11 postnodals, respectively. In cardinale the posterior lobe of prothorax is "undulate, very projecting in the middle -this part subquadrangular (. . .) without any incision in the center" (OSUNA, in litt., translated from Spanish) in fluviatile sp. n. the posterior margin of prothorax is more or less straight, with a small central notch. The ovipositor extends to beyond the end of segment 10 in cardinale, but hardly reaches the posterior margin of this segment in fluviatile sp. n.. Both species, however, lack the mesepisternal fossae.

Discussion

The species here described as new, and attributed to the genus Oxyagrion Selys could fit also in Acanthagrion Selys, for these two genera are not neatly separable (DONNELLY & ALAYO, 1966; COSTA, 1978). The retention of Acanthagrion appears to be a practical convenience rather than a taxonomic need based on morphological evidence.

Same characteristics, which currently are considered proper to the genus Oxyagrion are: the red colouration (in the male), the lack of postocular spots, the absence of extended black areas on head and mesepisternum, and the frequent presence of dark stippling on these parts; the more or less clearly bilobate apex of penis, the absence of mesepisternal fossae in the females of some species; the exclusively South American distribution, with all centers South of the Amazon. On the other hand, the genus Acanthagrion may in a general manner, be characterized as follows. predominant colour is blue or green, postocular spots are present and well defined; black areas on the head and black stripes (dark brown in females) on the mesepisternum are the rule, dark stippling on head and thorax is absent; in the overwhelming majority of species the distal penis segment is not bilobate; mesepisternal fossae are present in all known females; the distribution of the genus reaches from Mexico to Argentina, with most centers in the Amazonian and in the circumamazonian (Andean) region.

There are, however, species which do not fit neatly either in one or the other genus, forming "intermediates": Acanthagrion ablutum Calvert doesn't have clearly defined postocular spots, and in the female the occiput is stippled with brown In A. hermosae Leonard the postocular spots are entirely wanting, while the synthorax and the abdomen are marked with "deep cherry red" (LEONARD, l.c ). A. chararum Calvert is another species with ill-defined postocular spots. Similarly the genus Oxyagrion includes several species, which fall beyond the "typical" pattern and would fit in Acanthagrion as well: O. cardinale has a predominantly blue colouration and lacks any stippling on head and thorax. O. fluviatile sp n. is sky blue in both sexes. O. egleri Santos, originally attributed to Acanthagrion, is morphologically a perfect Oxyagrion (SANTOS in COSTA, 1978, p. 40), but is the only red species of this genus distributed from the Amazon northwards: Belém Brazil (SANTOS, 1961), French Guyana and Surinam (GEIJSKES, 1971), Venezuela (DE MARMELS, 1982).

I'm attributing fluviatile sp. n to the genus Oxyagrion because of the obsolescent postocular spots, the absence of black colour on head and thorax in both sexes, the stippling on the occiput, the lack of mesepisternal fossae and the deeply bilobate distal penis segment. The blue colouration of both sexes, as well as the northern distribution, are not in accordance with this proceeding.

Unfortunately the male of O. cardinale is unknown. O. fluviatile sp n. can not, therefore be compared properly with that species, which appears to be the only close relative. The bilobate penis of fluviatile sp. n. is somewhat similar to that of A. minutum Leonard, from which it differs however, in almost any other aspect. In several species of Oxyagrion the distal penis segment is fairly similar, too. The shape of the laminae mesostigmales and the interlaminal sinus of the female recall the same parts in A. ablutum. The anal appendages of the male resemble those of A. taxaense Santos.

Habits

After an unpublished observation by the late Prof. Dr. J. Racenis O. fluviatile sp. n. prefers the gallery forests, which border the rivers in the Venezuelan "llanos" (plains). The species is never common and rather solitary. Its flight is slow and, if disturbed, it tries to hide itself among dense vegetation. O. fluviatile sp. n. is, however, not restricted to the plains, but has been caught at higher elevations as well: Bejuma (670 m), Guatopo (700 m), San Cristóbal (830 m).

Acknowledgments

I am indebted to Prof. Dr. E. Osuna, Maracay for the examination of the type of O. cardinale Fraser, at the British Museum of Natural History (BMNH). His remarks, figures and colour transparencies were of invaluable help. Dr. Barnard of the BMNE kindly made the type accessible.

References

COSTA, J. M., 1978. Revisao do género Oxyagrion Selys, 1876 (Odonata Coenagrionidae). Publçoes avuls. Mus. nac. Rio de J. 61:1-216, 39 plates. 

DE MARMELS, J., 1982. Hallazgos de Odonata nuevos para Venezuela o poco conocidos. 2 . Bol. Ent. Venez. N.S. 2(15):114-116. 

DONNELLY, T. W. & P. Alayo, 1966. A new genus and species of Damselfly from Guatemala and Cuba (Odonata:Coenagrionidae). Fla. Ent. 49(2):107-114. 

FRASER, F. C., 1946. Notes on Amazonian Odonata in the Leeds Museum. Trans. R. Ent Soc. Lond. 96(2): 1145.

GEIJSKES D. C., 1971. List of Odonata known from French Guyana, mainly based on a collection brought together by the mission of the "Muséum National d'Histoire Naturelle", Paris, (1), (2). Ann. Soc. ent Fr. (N. S.) 7(3):655-677.

LEONARD, J. W., 1977. A Revisonary Study of the Genus Acanthagrion (Odonata Coenagrionidae). Misc. Publ. Mus. Zool. Univ. Mich. 153:1-173.

RACENIS, J., 1966. Preliminary List of Venezuelan Odonata. Inst. Zool. trop. Univ. Centr. Venezuela, Caracas, 16 pp. (mimeographed).

SANTOS, N. D. dos, 1961. "Acanthagrion egleri" sp. n. (Coenagrionidae: Odonata). Bol. Mus Paraense Emilio Goeldi, nova ser., zool. 38:1-5.

Figs. 1-9

Figs. 1-9. Oxyagrion fluviatile sp. n.: (1) abdomen (holotype) dorsal. view; (2) segment 10 wide anal appendages (hololype), left lateral view; (3) same (paratype 14384), dorsal view; (4) same (paratype 9072), posterior view; (5) head (paratype 4218), dorsal view; (6) end of abdomen (paratype 14385), left lateral. view; (7) region of prothorax and mesostigmal laminae (14385), right lateral. view; (8) same, dorsal view; (9) right wings of paratype (4221).

Figs. 10-15

Figs. 10-15. Oxyagrion cardinale Fraser (♀ holotype): (10) end of abdomen, left lateral view (the sharp ventral spine on segment 8, mentioned by Fraser, has apparently been broken off, end is not visible); (11) region of prothorax and mesostigmal laminae, right lateral view; (12) same, dorsal view, (12a) posterior lobe of prothorax, dorsal view, from slightly frontally; (13) entire specimen, glued on a card board, with type label of the BMNH; (14) anterior parts (glue visible on the venter); (15) wings. - All photographs and figures of this species have been realized by Dr. E. Osuna.