Art. XXXI.—The Occurrence in New Zealand of Myriapoda of the Genus Scutigerella, Order Symphyla.
[Read before the Philosophical Institute of Canterbury, 2nd December, 1914.]
The group Symphyla is of considerable interest and importance, for, as its name, given so appropriately by Ryder,* implies, it forms a connecting link between two classes of animals—the Insecta and the remainder of the Myriapoda The characters which indicate insectan affinities are the number and arrangement of the mouth-parts, and the presence, at the base of the legs, of small processes called exopods. The insects which show these characters are the simplest and most primitive groups—Thysanura and Collembola—a significant fact, for similarity of structure, in primitive, unspecialized forms of two groups is more likely to indicate affinity than resemblances in highly specialized and otherwise extremely differentiated forms.
The Symphyla contain two genera, Scolopendrella and Scutigerella, the species of which have been found in most parts of the world, but not hitherto from either Australia or New Zealand. Dr. H. J Hansen, of Copenhagen, who has written a monograph on the Symphyla,† stated in a letter, dated 2nd November, 1903, to Dr. Chilton that he had had no specimens from New Zealand or Australia, and suggested that search would show that several forms of Symphyla would certainly be found in both of these countries. Dr. Hansen's opinion has now been confirmed as far as New Zealand is concerned.
The specimen I am describing in this paper was among some Myriapoda from Ben Lomond, Lake Wakatipu, collected by Mr. T. Hall, and forwarded
[Footnote] * Ryder, F. A. Amer. Naturalist, vol. 14, pp. 821, 832, 1880.
[Footnote] † Hansen, H. J. Q.J.M.S., vol. 47, pp. 1–101. pl. 1–7, 1904.
to me by Dr. Chilton. It agrees very closely with the description given by Hansen (loc. cit.) of Scutigerella caldaria Hansen, but differs in the number of joints of the antenna. This will be referred to in the description given below.
Scutigerella caldaria was described from specimens found in hothouses in Copenhagen and Paris. Dr. Hansen had specimens of this species from South America also, and he states (loc. cit.) that the South American specimens very probably belong to the original form from which the specimens in the European hothouses have descended.
The presence of the same species in New Zealand also is another of the now fairly numerous examples of an animal whose means of distribution are limited being found in New Zealand and South America, and is further contributory evidence of the former existence of a land connection, probably by way of the Antarctic Continent, between these two countries.
Scutigerella caldaria Hansen. (Figs. 1–6.)
Scutigerella caldaria Hansen, Q.J.M.S., vol. 47, p. 36, pl. 2, figs. 3a–3g, 1904.
Head.—Seen from above broad, anterior margin straight, postero-lateral angles rounded
Antennae (figs. 2 and 3).–Segments 44 in number. The setae on the inner side of the proximal whorls not longer than those on the outer side. The secondary whorl beginning on the 11th joint, the upper whorl commencing on the 25th segment. The terminal segment with one large and one small striped organ, both on low protuberances. Hansen states that there are from 23 to 28 antennal segments, and that the secondary whorl commences on the 7th segment. The specimen I have described is much larger than those Hansen described—his were from 2·8 mm. to 4 mm., mine is 6·5 mm.—and, taking this into consideration. I do not think that the
number of the antennal segments alone would be a sufficient reason for making a new species. Further, the secondary whorl of setae commences at one-quarter of the length of the antennae in each case.
Legs.—The last pair (fig. 6) with tarsus five times longer than deep. The metatarsus with 5 or 6 and the tarsus with 7 spines on the outer dorsal row; the setae increase gradually a little in length from the base to the end of each joint, but the longest setae are shorter than half the depth of the metatarsus. The first pair of legs (fig. 5) with the anterior claw (fig. 4) elongate, moderately slender, and a little curved; the other claw moderately slender and a little more than half as long as the anterior one.
Cerci with numerous short setae, of which the distal ones are not half as long as the depth of the cerci.
Hab.—South America, New Zealand, and Europe (? introduced).
Locality of New Zealand specimen, Ben Lomond, Lake Wakatipu, Central Otago.
Length, 6·25 mm.