Genus Parachaetoceras nov.
Genotype: Chaetoceras pritchardi (Womersley, 1936).
In his description of the species Chaetoceras pritchardi Womersley refers to the fact that the species differs from all known members of the genus in possessing well-developed dental spines, and, although placing it in the genus Chaetoceras, at the time he mentions that it may be necessary to erect a new genus for its reception, when more material has become available. I now have examined many specimens from all over the North Island, and, after studying Handschin's description of the genus Chaetoceras, I am definitely convinced that the New Zealand species requires the erection of a new genus for its reception. Accordingly, I propose the name Parachaetoceras for this new genus characterized by—Antennae over twice the length of the body and bearing ventrally many long setae which often are as long as or longer than a segment; dens with a single row of stout, simple spines. On the body are many long, narrow, flattened ciliated scale-like setae. Ant. IV annulated.
The genus differs from Chaetoceras Hand. in the possession of dental spines and the peculiar scale-like setae.
Parachaetoceras pritchardi (Womersley, 1936). Plate 67, figs. 456–460.
1936. Chaetoceras pritchardi Womersley.
Colour: Creamy-white to yellowish, with irregular patches of blue on sides of body and head. A dorsal, longitudinal brown stripe generally present. Legs and antennae blue to violet, ochreous at joints. Furcula yellow. Ocelli on black fields.
Clothing: With short, scale-like ciliated setae dorsally on thorax and abdomen. Numerous long ciliated setae on posterior part of abdomen and long flexed setae prominent on dorsal surface of head, thorax, and anterior portion of abdomen. On ventral surface of antennae and on legs are numerous very long simple setae. Furcula with many ciliated setae.
Body: Length up to 4.0 mm. Antennae about twice as long as body, the segments variable in length, but III is always shorter than IV. Ant. IV annulated. Ocelli, eight to each side, all large and equal. Abd. IV 4–5 times as long as Abd. III.
Legs: Claw with a pair of large outer lateral teeth and two inner teeth, one at about one-third and the other at two-thirds. Empodial appendage lanceolate, reaching to distal inner tooth of claw. A single clavate tenent hair as long as claw to each foot.
Furcula: Reaching forward to head. Dens half as long again as manubrium and bearing a single row of simple spines. Mucro indistinctly separated from dens and bidentate, the teeth approximately equal. The dens apically bears two long spine-like appendages which are easily rubbed off, but if absent the marks of their attachment can be plainly seen.
Localities: Originally reported by Womersley from among fallen leaves at Niger Bay, Hillsborough, Auckland, where it was collected by Mr. E. D. Pritchard. I now can add further localities which include Paiahia and the Bay of Islands, in debris under manuka scrub; Waipoua Kauri Forest and Trounson's Kauri Park, North Auckland, in leaf debris; Blue Lake, Rotorua, in leaf mould; throughout the Urewera Country, in leaf debris in the forests; Morere Springs, nikau forest, in leaf debris; Te Kuiti, in leaf debris; Lake Rotoma, Rotorua, in leaf debris.
Remarks: The peculiar scale-like setae found on this species are interesting as throwing some light on the possible means of evolution of the typical ribbed and striated Collembolan scale from the equally typical ciliated setae. In these long, narrow, flattened setae all the cilia have migrated to the surface, the outer surface, and by further enlargement, accompanied by a broadening of the setae and a fusion of the cilia, a structure similar to a Lepidosira scale could result. Further modification of the cilia structure could quite conceivably produce a ribbing such as is found in the scales of Lepidophorella, while reduction of the cilia structure could result in the formation of a hyaline scale such as is found in many Collembola. I suggest that it is along such lines that the scales of Collembola have developed.
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Hypotype: Slide 3/54, Dominion Museum Collection.