Tuatara: Volume 10, Issue 3, September 1962
A Key to the — New Zealand Harvestmen—Part I
A Key to the
New Zealand Harvestmen—Part I
The harvestmen (Order Opiliones) are often confused with the spiders (Order Araneae). Unfortunately the misleading name “harvest spiders’ is often used for them, based on the very superficial likeness they have to spiders. A number of simple characters will immediately separate a spider from a harvestman.
Harvestmen do not use silk and therefore spinnerets are absent. The cephalothorax and the abdomen of a spider are joined by a thin waist and the abdomen (except in a few extremely rare overseas forms) is not segmented. A harvestman is always characterised by a broadly oval body without any constriction and the abdominal, and often thoracic, segmentation is clearly visible. This segmentation also differentiates the small harvestmen, particularly the S.O. Cyphophthalmi from the mites.
The Order Opiliones is divided into three sub-orders—Cyphophthalmi (mite-like harvestmen), Palpatores (longlegged harvestmen), and Laniatores (shortlegged harvestmen), all of which are abundantly represented in New Zealand. Generally speaking they are found in forest although a few species, particularly the Palpatores, are also found in grassland and sub-alpine areas and in the South Island among the shingle banks of the larger East Coast rivers. The Northern Hemisphere Phalangium opilio is the commonest species found in open country and in gardens throughout New Zealand but this species has never been found in native bush.
The systematic analysis of the New Zealand harvestmen has brought to light a number of interesting features which need further investigation, probably the most interesting of which is polymorphism. Most of the New Zealand Palpatores (and also those of Australia and South Africa) are characterised by an extraordinary difference in appearance between the male and female. The males are usually black, the carapace is hard and the chelicerae are enormously developed, while the females are soft-bodied, brownish animals with short inconspicuous chelicerae. It appears that the male chelicerae in a single species may vary considerably in size and form but whether this variation is of a graded nature or polymorphic has yet to be established. It is, however, clear that in the Laniatores page 130 polymorphism is a common feature among the males of many species. In New Zealand species the male: female ratio is usually approximately 1 : 1 whether male dimorphism occurs or not. Where male dimorphism does occur the ratios of the two forms of males appear to suggest simple arithmetical ratios, e.g. 1 : 1, 2 : 1, 4 : 1. There has been no study made of the sex chromosome mechanism of the Laniatores but it seems probable that a multiple sex chromosome mechanism is present as is commonly found in other arachnids.
Certainly the detailed study of polymorphism in the New Zealand harvestmen would be a most fascinating field.
The key has been constructed as far as possible to lead the user through the major taxonomic divisions to genera. In some of the larger genera, particularly Nuncia, it may be advisable to refer directly at this stage to The New Zealand Harvestmen (Forster 1954). In order to identify certain species it is necessary to examine the male genitalia.
The removal of the genitalia is a simple procedure using two needles. If slight pressure is put on the base of the operculum it will lift. enabling the second needle to be inserted into the cavity. This needle is then used to gently cut down one side from the opening to expose the genitalia which can then be lifted out.
In many cases the characters used in the key to separate species are secondary sexual ones possessed only by males and therefore it is not possible to identify females of these species from the key, which should however lead the user to the correct genus.
A number of species were described by Hogg (1909, 1920). Loman (1902). Phillipps and Grimmett (1932), Pocock (1903), Roewer (1931) and Simon (1899). These are indicated in the key, and the relevant bibliography is given in The New Zealand Harvestmen (Forster, 1954). All species not otherwise indicated are attributable to Forster.
Mite-like harvestmen with scent glands opening from a prominent conical tubercle on the cephalothoracic carapace. Eye absent in New Zealand species. Genital opening without an operculum (fig. 26). Tarsus 4 of male distended with a spur on dorsal surface (fig. 16). Sub-order Cyphophthalmi.—3
Not mite-like, openings of scent glands not placed on a tubercle and difficult to see. Two eyes usually placed on a median eyemound (fig. 30). Genital opening covered by an operculum. Tarsus 4 not modified.—2
Figs. 1, 2: Ventral and dorsal surface of a typical short-legged harvestman (Hendea). Fig. 3: Sternum typical for tribe Adaeini. Fig. 4: Sternum typical for tribe Triaenobunini. Fig. 5: Male chellcera Megalopsalis sp. (in many species the second segment is not distended). Fig. 6: Trochanter and femur of Rakaia sp. showing ventral process on trochanter. Fig. 7: Typical palp of a long-legged harvestman (S.O. Palpatores). Figs. 8, 9: Typical chelicera of short-legged harvestman.
Long, slender legs, pedipalp weak, leglike (fig. 7) genital operculum not hinged at base (fig. 25). Tarsi of legs 3 and 4 with a single simple claw. Body usually soft. Chelicerae of males often tremendously developed (fig. 14). Sub-order Palpatores (the long-legged harvestmen). — 29
Legs relatively short and strong. Pedipalp strongly developed and armed with strong spines (fig. 5), (except family Synthetonychidae, fig. 8). Tarsi of legs 3 and 4 with either two claws or a modified single claw (figs. 18-21). Genital operculum with a definite suture at base where it is hinged (fig. 1). Body hard. Sub-order Laniatores (the shortlegged harvestmen). 32
Tarsus 4 of male with single segment (fig. 17) (Genus Rakaia). — 4
Tarsus 4 of male with two segments (fig. 16). (Genus Neopurcellia). — 27
Ventral process present on trochanter of pedipalp (fig. 6). — 5
Ventral process absent from the trochanter of the pedipalp. — 16
Tarsal spur terminating bluntly. — 6
Tarsal spur terminating sharply. — 7
Tarsal spur one-sixth the length of tarsal segment. Rakaia sorenseni
Tarsal spur one-third the length of tarsal segment. Rakaia sorenseni digitata
Posterior portion of abdomen with single median scopula. — 8
Posterior portion of abdomen with two or more scopulae. — 13
Tarsus IV elongate, at least three times as long as greatest depth. — 9
Tarsus IV pyriform, no more than twice as long as greatest depth. — 11
Length of body 3 mm. or more. — 10
Length of body less than 2.5 mm. Rakaia uniloca
Tergite VIII appearing as a ledge with two ovoid tubercles directed towards each other. Rakaia magna magna
Tergite VIII divided by a broad median V. Rakaia magna australis
Tarsal spur relatively short and stout. — 12
Tarsal spur long and slender. Rakaia solitaria
Tergite VIII when viewed from below evenly rounded on each side of a narrow median groove. Rakaia media
Tergite VIII when viewed from below seen as a pair of pronounced tubercles bounding a broad median groove. Rakaia media insula
Fig. 10: Typical palp of a short-legged harvestman (Hendea). Fig. 11: Palp family Synthetonychidae. Figs. 12-14: Male genitalia Hendea sp.
Scopula present on the posterior margin of the anal plate. - 14
Scopula absent from the posterior margin of the anal plate. - 15
Tarsal spur long and slender; directed parallel to the tarsal segment. Rakaia antipodiana Hirst, 1925
Proximal portion of the tarsal spur stout and erect, becoming slender distally where it is directed parallel to the tarsal segment. Rakaia pauli
Tarsus IV twice as long as greatest depth; tarsal spur erect. Rakaia dorothea (Phillipps and Grimmett, 1932)
Tarsus IV two and a half times as long as greatest depth; tarsal spur sloping forward. Rakaia solitaria
Anal plate entire.—17 Anal plate deeply indented posteriorly. Rakaia stewartiensis
Scopulae present on the posterior portion of the abdomen. - 18 Scopulae absent from the posterior portion of the abdomen. - 25
Tarsus IV less than two and a half times as long as greatest depth. -19
Tarsus IV more than three times as long as deep; tarsal spur present as a strong spinous process one-third the length of the tarsal segment. Rakaia longitarsa
Tarsal spur with a rounded protuberance at the base. 20 Tarsal spur evenly conical at the base.—21
Length of body 2.0 mm. Rakaia denticulata denticulata Length of body 2.63 mm. Rakaia denticulata major
Tarsal spur long and slender.—22 Tarsal spur relatively short.—23
Tergite VIII with a broad median groove; not swollen posteriorly. Rakaia inerma inerma
Posterior portion of abdomen with well-developed lobes. Rakaia inerma stephenensis
Scopulae present on the posterior margin of the anal plate. - 24
Scopulae absent from the anal plate. Rakaia crypta
A pair of scopulae present on the inner lateral surface of tergite VIII; tarsal spur directed parallel to the tarsal segment but bent down at the tip. Rakaia healyi
Scopulae absent from the inner lateral surfaces of tergite VIII; tarsal spur short, directed obliquely forward. Rakaia lindsayi
Tarsus IV granulated; apex of tarsal spur excavated to form a thin hood. Rakaia granulosa
Tarsus IV smooth; tarsal spur not excavated.—26page 135
Dorsal ridge of basal segment of chelicera sharp and directed well back; swelling present at the base of tarsal spur. Rakaia calcarobtusa
Dorsal ridge of basal segment of chelicera evenly rounded, slightly directed back; tarsal spur uniform.
Rakaia calcarobtusa westlandica
Fig. 15: Leg Hendea sp. Fig. 16: Metatarsus and tarsus of male Neopurcellia salmoni. Fig. 17: Metatarsus and tarsus male Rakaia antipodiana. Fig. 18: Double claw tarsus 3 and 4 fam. Phalangodidae. Fig. 19: Claw tarsus 3 and 4 sub-family Soerensenellinae. Fig. 20: Claw of tarsus 3 and 4 sub-family Triaenonychinae. Fig. 21: Claw of tarsus 3 and 4 Fam. Synthetonychidae. Fig. 22: Male genitalia Nuncia (Corinuncia) cockayni. Fig. 23: Male genitalia Nuncia (Nuncia) obesa.
Trochanter of pedipalp with a ventral process. Body very small, no more than 1.7 mm. in length. Neopurcellia minutissima
Trochanter of pedipalp without ventral process. Body no less than 2.2 mm. in length.—28
Two scopulae present, one originating from each inner margin of the posterior tergal tubercles. Neopurcellia salmoni
A single median scopula present, originating from the posterior margin of the anal plate. Neopurcellia florensis
Relatively large harvestmen, body length not less than 6 mm. usually much bigger. Eyemound rounded, diameter less than one quarter of width of cephalothoracic carapace; pedipalps leglike, without tubercles. Family Phalangiidae.—30
Minute, body length about 1 ½ mm. Eyemound greatly developed as wide as cephalothoracic carapace (fig. 24). Pedipalps with spinous tubercles. (Family Acropsopilionidae.) Rare leafmould dwellers. One species. Zeopsopilio neozelandiae
Body rounded and soft.—31 Body flattened and hard. - 169
Undersurface of body silvery white. (An introduced European species found throughout New Zealand but not in forest.) Chelicerae of both male and female small, but male chelicera with strong erect projection on proximal surface of second segment. Phalangium opilio L.
Undersurface of body occasionally white but never silvery white. Males with long conspicuous chelicera which may be up to four times the length of the body. Females predominantly grey or brown, chelicerae small, inconspicuous. Subfamily Phalangiinae.
Palp with a spur on the distal end of the patella.
Palp without spur. Pantopsalis
There are twelve species placed in these two genera. Unfortunately because sexual dimorphism was not taken into account when the recorded species were established and also because a large number of species remain undescribed no attempt has been made to key out the described ‘species’. (See Rec. Dom. Mus. 1944, 1: 183-92.)
(To be continued)page 137