Genus Achorutes Templeton.
Achorutes armatus Nicolet, 1841.
This species may now be considered as generally distributed throughout the country and very common. An interesting locality was on the surface of a swimming pool in Auckland, collected by W. Cottier.
Achorutes longispinus Tullberg, 1876.
This species was collected recently from foliage at Red Rocks, Cook Strait, by R. Forster.
Achorutes pseudopurpurascens Womersley, 1928.
Like armatus, this species can now be regarded as common and generally distributed throughout the country.
Achorutes morbillatus Salmon, 1941.
Now reported from the North Island being taken under the bark of beech trees at Akatarawa by R. Forster.
Achorutes rossi Salmon, 1941.
Recently this species was brought to me as doing damage in a garden at Karori, Wellington, where it appeared in such enormous numbers that it could be swept up by the bucketful from the concrete paths, around and under which it apparently was breeding. It was controlled by application of nicotine sulphate.
Achorutes viaticus Tullberg, 1872.
Bagnall in 1941 studied the viaticus group of Achorutes in England, and set up two new species, separating the true viaticus of Tullberg from the others as being the only one of the group with the rami of the tenaculum bearing four teeth. Recently my attention was focussed on this by the discovery of a species of the viaticus group forming a black scum over brackish pools among the rocks at Rocky Bay, Titahi Bay, Wellington. This proved to be a new species, with the rami of the tenaculum bearing only three teeth. Re-examination of the other New Zealand material previously reported by me as being Achorutes viaticus Tullb., reveals that this is not the true viaticus as shown by Bagnall, but belongs also to the new species, which I am calling A. titahiensis. In 1909 Carpenter
reported A. viaticus from Macquarie Island, but whether this was the true viaticus or not cannot be fixed from his published statement, and the specimens upon which he based his identification are not available.
Achorutes titahiensis sp. nov. Plate 40, figs. 12–21.
[Achorutes viaticus Tullb. (in part), Salmon 1937, 1941, not of Tullb.]
Colour: Black all over.
Clothing: Evenly clothed with short setae, which are bent over at one-third along their length and sometimes apically serrated. These are interspersed with longer, straight, stout setae, which are finely serrated on their apical half. The long setae on Abd. IV 0.3 the length of the segment.
Body: Length up to 1.75 mm. Antennae shorter than the head. Ant. IV apically with sensory knob in pit, accessory cone with sense rod and three slightly curved sensory setae. Ant. III with sensory organ situated near joint with fourth segment, and consisting of two sense clubs, each arising from a small pit and separated from each other by a low cuticular fold; the whole flanked on either side by a longer, straighter sense rod. The sense rod on one side is very much more removed from the sense clubs than is the other. Ocelli eight to each side, all equal. Postantennal organ larger than an ocellus, with central boss and 4–5 peripheral lobes. Abd. VI with a pair of small, slightly curved anal spines, each on a basal papilla about one-third to one-half the length of the spine; the spines without the papillae one-fourth to one-fifth the length of the hind claw. Papillae of anal spines may be touching basally or separated up to one and a-half times the width of their bases. Rami of tenaculum each with three teeth.
Legs: Claw with one prominent inner tooth at about half way down, and a pair of small outer teeth, one to each side at about one-quarter back from apex. Empodial appendage needle-like, from half to two-thirds length of claw, with narrow outer lamella and broad inner lamella reaching approximately halfway down. Tenent hairs weakly clavate, in line across the foot, with two to the front feet and three to each of the others, the central one tending to be longer and stouter than the other two.
Furcula: Mucrodens and manubrium of approximately equal length. Dens with one very long basal seta and 5–6 shorter setae. Mucro strongly curved, with apical blunt tooth and broad inner basal lamella, which may be plain but generally carries a sharp and deep incurve at ⅔ from base. Usually there is a smaller, very blunt tooth-like projection in the centre of the apical curve of the lamella. Basal portion of the lamella frequently wavy.
Localities: Titahi Bay, forming a black scum on the surface of brackish pools among the rocks, Rocky Bay; Island Bay, Wellington, amongst the roots of tidal grasses; Silverstream, South Karori, under stones in the stream bed (Author's Coll.); Papanui. Christchurch, on the surface of an unused well (Coll. E. W. Moore).
Type: Slide 3/1216 and Figured Paratypes Slides 3/1205 and 3/1214, Dominion Museum Collection.