Art. XXXIV.—Description of a New Dragon-fly belonging to the Genus Uropetala Selys.
[Read before the Nelson Institute, 23rd December, 1920; received by Editor, 31st December, 1920; issued separately, 8th August, 1921.]
Through the much-appreciated kindness of Dr. C. Chilton, Professor of Biology at Canterbury College, Christchurch, I was enabled, during the summer of 1919–20, to spend a few days at the Cass Biological Laboratory. In company with Dr. Chilton and Mr. Charles Lindsay, of the Canterbury Museum, I collected a number of dragon-flies from the streams around Cass; later on I obtained a number of the same species from Arthur's Pass. In both localities a large Uropetala was seen flying about, and a number of specimens of both sexes were obtained. At first I took this fine dragon-fly to be Uropetala carovei White, recorded from many localities in New Zealand, and also being the only known member of the genus. Later on, however, I obtained specimens of Uropetala from Lake Wakatipu, and also from the North Island, which in many characters did not agree with those taken at Cass and Arthur's Pass. It became evident that there were two species of Uropetala present in my collections, one of which agreed closely with the descriptions given by White and de Selys for U. carovei, while the other was undescribed. It is this latter species which occurs at Cass and Arthur's Pass.
While at Cass we located an area in a small mountain-swamp where the holes made by the larvae of this dragon-fly were abundant. By merely inserting one's fingers into these holes, which are made in peaty soil, and are about ½ in. in diameter, and by working one's hand downwards, enlarging the hole at the same time, until a depth of from 10 in. to more than 1 ft. is attained, the larvae can be felt as hard inert objects at the bottom, and can be hauled out with ease. Unlike the larvae of U. carovei, which, as far as my experience goes, are very fierce and liable to snap at one's fingers when handled, these larvae were very inert, and could be handled with safety. As the last three instars were obtained, this habit is not likely to be due to the approach of ecdysis for more than fifty larvae were taken out and handled. I hope later on to make a careful comparative study of these two larval forms, with a view to the discovery and recording of any morphological differences that may be present. In the meantime, Mr. W. C. Davies, Curator of the Cawthron Institute, has very kindly offered me an excellent photograph of the larva of U. carovei, taken from a specimen found in the Wairarapa district, for publication in this paper. From this photograph, which is reproduced in Plate LIII, a very good idea can be obtained of the general appearance of these larvae. As far as I know, no accurate figure has yet been published of the larva of U. carovei, and I wish to thank Mr. Davies for this excellent photograph.
I wish to dedicate this new species, whose description follows, to Dr. Chilton as a memorial of the excellent work which he has done, and is doing, in connection with the Cass Biological Station.
Uropetala chiltoni n. sp.
♂. Total length, 83 mm.; abdomen, 60mm.; forewing, 49 mm.; hindwing, 47 mm.; expanse, 102 mm.
General shape exactly as in U. carovei.
Head.—Eyes dark brown, the inner portion of the orbits blackish, the outer marked with a yellowish line. Occiput broadly yellow, as in U. carovei. Vertex black, the three ocelli brown. Frons yellow above, but with the black colour of the vertex encroaching basally for a short distance, as shown in text-fig. 2b; anterior portion of frons broadly yellow, this colour encroaching very slightly upon the upper portion of the postclypeus. Postclypeus and anteclypeus both black; genae yellow. Labrum with black margins surrounding a pair of partially fused subrectangular blocks of yellow, separated above only by a downward-projecting, short, median bar of black. Labium brown The colouring of the facial portion of the head is shown in text-fig. 2a
Colour-pattern of head in Uropetala.
Uropetala carovei White: Fig. 1a, face; fig. 1b, upper portion of frons.
Uropetala chiltoni n. sp.: Fig 2a, face; fig. 2b, upper portion of frons.
ac, anteclypeus; ant, antenna; fr, upper portion of frons; fr', anterior portion of frons; g, gena; lr, labrum; pc, postclypeus.
Thorax.—Prothorax small, dark brown, hairy. Synthorax blackish brown, with paired dorsal and lateral stripes of yellow, very similar to those seen in U. carovei. The dorsal stripes are, however, broader than those in U. carovei, and stand closer to one another towards the middle line, leaving a narrower band of blackish brown along the mid-dorsal carina. The metanotum and lower part of the mesonotum are densely clothed with grey hairs, and similar hairs extend down on to the dorsal part of the first abdominal segment, and less abundantly on to the second also. Breast covered with long grey hairs. Legs entirely black. Wings as in U. carovei
Abdomen.—Shape narrow-cylindrical, segments 1–2 broader than the rest. Sides of 1–2 less hairy than in U. carovei, the edges of the lateral sheaths bordering the genital fossa almost hairless; in U. carovei the hairs on these parts are very distinct. Colour dark brown shading to black, with
a pair of large basal yellow spots on each segment from 2 to 8; these spots are larger, squarer, and stand more closely together than do the corresponding spots in U. carovei. Segments 9–10 black, a brown mark low down on each side of 9, and a yellowish transverse line bordering the suture between it and 8; 10 with a pair of brown spots high up on the sides. Appendages: Superiors broadly black, foliate, as in U. carovei; inferior shorter, subtriangular, upcurved, downy beneath, blackish brown, tip very distinctly truncate, more so than in U. carovei.
♀. Slightly larger and stouter than ♂; general shape and coloration closely similar to that of ♂, but the upper part of the frons has the black colour encroaching upon it medially as a broadly triangular blotch, and the spots of the abdomen are considerably larger than in the ♂. Appendages short, 1 mm., black, separated by a brownish, downy tubercle.
Types.—♂ (holotype) and ♀ (allotype) taken together at Arthur's Pass, 19th January, 1920, and placed in the Cawthron Institute collection, which also contains a series of paratypes from the same locality.
Habitat.—Arthur's Pass and Cass, N.Z.
The specimens taken at Cass had only recently emerged, and were not in as good a condition for descriptive purposes as those taken a week later at Arthur's Pass; hence I have chosen the types from the latter series. It should be noted that all parts described here as yellow were in life pale creamy-yellow, not the rich lemon-yellow associated with mature examples of U. carovei. Possibly the new species assumes the deeper yellow colouring with advancing age, but we cannot be certain of this at present; it may equally well be that the creamy colour of the markings is a specific character.
Before deciding to describe this new species the specimens were taken to Europe and carefully compared with the specimens of U. carovei in the British Museum and in the de Selys collection at the Brussels Museum. This comparison established the fact that the specimens from Arthur's Pass and Cass were very distinct from any of the specimens of U. carovei in these collections. Whether the differences are of true specific value, or only indicate a subspecies or geographical race, it is not easy to decide; but they are so well marked, and so constant over the whole series of forms examined, that I have decided to consider them as of specific value.
The main differences between U. carovei White and U. chiltoni n. sp may be summed up as follows:—
The two species can at once be separated by the very distinct colour-patterns of the head, as may be seen from text-figs. 1 and 2. In U. carovei the labrum is entirely black, and the frons has much less yellow on it than in U. chiltoni; the manner in which the black encroaches on the frons both from above and below, in the case of U. carovei, is well shown in text-fig. 1. It should, however, be noted that, in the case of the females only, the pattern of the upper part of the frons is somewhat similar in both species.
On the thorax the dorsal bands are wider in U. chiltoni; also, the femora of this species are black, those of U. carovei being either brown or yellowish.
On the abdomen the arrangement and colour of the hairs at the base is very characteristic of each species, as already shown in the description, while the yellow spots in U. chiltoni are distinctly larger, squarer, and closer together than those in U. carovei. The appendages are closely similar in general appearance, but in the male of U. chiltoni the inferior appendage is distinctly more truncate at the tip than in U. carovei.
As the large and conspicuous dragon-flies belonging to the genus Uropetala appear to be common in many parts of New Zealand, it should not be a difficult matter to work out the distribution of the two species if collectors will send along specimens from new localities for determination. As long as there was supposed to be only one species present there was no inducement to do this. So far as known at present, U. carovei occurs over the whole of the North Island, and also in the Lake Wakatipu district of the South Island, while U. chiltoni occupies a middle position at Arthur's Pass and Cass. This suggests that U. chiltoni may possibly be the species that inhabits the west coast of the South Island, and that it may be encroaching upon the domain of the eastern species through the gap at Arthur's Pass. It would otherwise be difficult to explain the presence of the species typical of the North Island in a locality such as Lake Wakatipu. It is, in any case, clear that, as regards the genus Uropetala, each Island does not possess its own peculiar species, but that some other barrier than Cook Strait has operated to bring about the differences existing at present.